diff --git a/cmake/Modules/FindLHAPDF.cmake b/cmake/Modules/FindLHAPDF.cmake
new file mode 100644
index 00000000000..cf0dbe2fdbd
--- /dev/null
+++ b/cmake/Modules/FindLHAPDF.cmake
@@ -0,0 +1,56 @@
+# - Try to find LHAPDF
+# Defines:
+#
+#  LHAPDF_FOUND
+#  LHAPDF_INCLUDE_DIR
+#  LHAPDF_INCLUDE_DIRS (not cached)
+#  LHAPDF_LIBRARY
+#  LHAPDF_LIBRARIES (not cached)
+#  LHAPDF_LIBRARY_DIRS (not cached)
+
+if (LHAPDF_ROOT_DIR OR LHAPDF_DIR OR (DEFINED ENV{LHAPDF_ROOT_DIR}) OR (DEFINED ENV{LHAPDF_DIR}) )
+  set(LHAPDF_SEARCH_DIRS "" CACHE STRING "" FORCE)
+  if (LHAPDF_ROOT_DIR)
+    list (APPEND LHAPDF_SEARCH_DIRS "${LHAPDF_ROOT_DIR}" )
+  endif()
+  if (LHAPDF_DIR)
+    list (APPEND LHAPDF_SEARCH_DIRS "${LHAPDF_DIR}" )
+  endif()
+  if (DEFINED EVN{LHAPDF_ROOT_DIR})
+    list (APPEND LHAPDF_SEARCH_DIRS "$ENV{LHAPDF_ROOT_DIR}" )
+  endif()
+  if (DEFINED ENV{LHAPDF_DIR})
+    list (APPEND LHAPDF_SEARCH_DIRS "ENV{LHAPDF_DIR}" )
+  endif()
+endif()
+if (LHAPDF_SEARCH_DIRS)
+  find_path(LHAPDF_INCLUDE_DIR LHAPDF/LHAPDF.h PATHS ${LHAPDF_SEARCH_DIRS} PATH_SUFFIXES include NO_DEFAULT_PATH)
+  find_library(LHAPDF_LIBRARY NAMES LHAPDF PATHS ${LHAPDF_SEARCH_DIRS}  PATH_SUFFIXES lib lib64 NO_DEFAULT_PATH)
+else()
+  find_path(LHAPDF_INCLUDE_DIR LHAPDF/LHAPDF.h PATH_SUFFIXES include)
+  find_library(LHAPDF_LIBRARY NAMES LHAPDF PATHS_SUFFIXES lib lib64)
+endif()
+set(LHAPDF_VERSION 0.0.0)
+if (LHAPDF_INCLUDE_DIR)
+  if (EXISTS ${LHAPDF_INCLUDE_DIR}/LHAPDF/Version.h)
+    file(STRINGS ${LHAPDF_INCLUDE_DIR}/LHAPDF/Version.h LHAPDF_VERSION_STRING_CONTENT REGEX "^#define[ ]+LHAPDF_VERSION[ ]+\"" )
+    if (LHAPDF_VERSION_STRING_CONTENT)
+      string(REGEX MATCH "[1234567890\.]+[a-zA-Z]*" LHAPDF_VERSION ${LHAPDF_VERSION_STRING_CONTENT})
+    endif()
+  endif()
+endif()
+
+
+mark_as_advanced(LHAPDF_INCLUDE_DIR LHAPDF_LIBRARY)
+
+# handle the QUIETLY and REQUIRED arguments and set LHAPDF_FOUND to TRUE if
+# all listed variables are TRUE
+include(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(LHAPDF DEFAULT_MSG LHAPDF_INCLUDE_DIR LHAPDF_LIBRARY)
+
+set(LHAPDF_LIBRARIES ${LHAPDF_LIBRARY})
+get_filename_component(LHAPDF_LIBRARY_DIRS ${LHAPDF_LIBRARY} PATH)
+
+set(LHAPDF_INCLUDE_DIRS ${LHAPDF_INCLUDE_DIR})
+
+mark_as_advanced(LHAPDF_FOUND)
diff --git a/cmake/Modules/FindPythia6.cmake b/cmake/Modules/FindPythia6.cmake
index 110e934aa14..b4f115bfaf0 100644
--- a/cmake/Modules/FindPythia6.cmake
+++ b/cmake/Modules/FindPythia6.cmake
@@ -4,9 +4,17 @@
 # Defines:
 #  PYTHIA6_FOUND
 #  PYTHIA6_LIBRARIES
+set(TEST_PYTHIA6_ROOT_DIR  "" ${PYTHIA6_ROOT_DIR})
+IF(TEST_PYTHIA6_ROOT_DIR STREQUAL "")
+  IF(DEFINED ENV{PYTHIA6_ROOT_DIR})
+    set(PYTHIA6_ROOT_DIR  $ENV{PYTHIA6_ROOT_DIR})
+  else()
+    set(PYTHIA6_ROOT_DIR  "/usr")
+  endif()
+endif()
 
-find_library(PYTHIA6_LIBRARY NAMES Pythia6 pythia6-$ENV{PYTHIA6_VERSION}
-			     HINTS $ENV{PYTHIA6} $ENV{PYTHIA6}/lib)
+find_library(PYTHIA6_LIBRARY NAMES Pythia6 pythia6 pythia6-$ENV{PYTHIA6_VERSION}
+			     HINTS $ENV{PYTHIA6} $ENV{PYTHIA6}/lib $ENV{PYTHIA6}/lib64 ${PYTHIA6_ROOT_DIR}/lib ${PYTHIA6_ROOT_DIR}/lib64)
 
 set(PYTHIA6_LIBRARIES ${PYTHIA6_LIBRARY})                              
 #message(STATUS PYTHIA6_LIBRARIES ${PYTHIA6_LIBRARIES} )
diff --git a/cmake/Modules/FindPythia8.cmake b/cmake/Modules/FindPythia8.cmake
index 6a5e9d2f7e1..3b709392f6c 100644
--- a/cmake/Modules/FindPythia8.cmake
+++ b/cmake/Modules/FindPythia8.cmake
@@ -1,24 +1,51 @@
-# Locate Pythia8 library
-# in a directory defined via PYTHIA8 environment variable
-#
+# - Locate pythia8 library
 # Defines:
-#  PYTHIA8_FOUND
-#  PYTHIA8_LIBRARIES
-#  PYTHIA8_INCLUDES
+#
+#  Pythia_FOUND
+#  PYTHIA8_VERSION
+#  PYTHIA8_INCLUDE_DIR
+#  PYTHIA8_XMLDOC_DIR
+#  PYTHIA8_INCLUDE_DIRS (not cached)
+#  PYTHIA8_LIBRARY
+#  PYTHIA8_hepmcinterface_LIBRARY
+#  PYTHIA8_lhapdfdummy_LIBRARY
+#  PYTHIA8_LIBRARIES (not cached) : includes 3 libraries above; not to be used if lhapdf is used
+set(TEST_PYTHIA8_ROOT_DIR  "" ${PYTHIA8_ROOT_DIR})
+IF(TEST_PYTHIA8_ROOT_DIR STREQUAL "")
+  IF(DEFINED ENV{PYTHIA8_ROOT_DIR})
+    set(PYTHIA8_ROOT_DIR  $ENV{PYTHIA8_ROOT_DIR})
+  else()
+    set(PYTHIA8_ROOT_DIR  "/usr")
+  endif()
+endif()
 
-find_library(PYTHIA8_LIBRARY NAMES pythia8
-			     HINTS $ENV{PYTHIA8} $ENV{PYTHIA8}/lib)
+find_path(PYTHIA8_INCLUDE_DIR Pythia.h Pythia8/Pythia.h HINTS  ${PYTHIA8_ROOT_DIR}/include)
 
-set(PYTHIA8_LIBRARIES ${PYTHIA8_LIBRARY})
-#message(STATUS PYTHIA8_LIBRARIES ${PYTHIA8_LIBRARIES} )
+find_path(PYTHIA8_XMLDOC_DIR Version.xml HINTS  ${PYTHIA8_ROOT_DIR}/xmldoc  ${PYTHIA8_ROOT_DIR}/share/Pythia8/xmldoc ${PYTHIA8_ROOT_DIR}/share/pythia8-data/xmldoc  ${PYTHIA8_ROOT_DIR}/share/doc/packages/pythia/xmldoc )
 
-find_path( PYTHIA8_INCLUDES Pythia8/Pythia.h
-           HINTS $ENV{PYTHIA8} $ENV{PYTHIA8}/include $ENV{PYTHIA8}/include/Pythia8 )
-set(PYTHIA8_INCLUDES ${PYTHIA8_INCLUDES})
+if(PYTHIA8_INCLUDE_DIR AND PYTHIA8_XMLDOC_DIR)
+  file(READ ${PYTHIA8_XMLDOC_DIR}/Version.xml versionstr)
+  string(REGEX REPLACE ".*Pythia:versionNumber.*default.*[0-9][.]([0-9]+).*" "\\1" PYTHIA8_VERSION "${versionstr}")
+  set(PYTHIA8_VERSION "8.${PYTHIA8_VERSION}")
+  find_library(PYTHIA8_LIBRARY NAMES pythia8 Pythia8 HINTS ${PYTHIA8_ROOT_DIR}/lib ${PYTHIA8_ROOT_DIR}/lib64)
+  find_library(PYTHIA8_lhapdfdummy_LIBRARY NAMES lhapdfdummy  HINTS ${PYTHIA8_ROOT_DIR}/lib ${PYTHIA8_ROOT_DIR}/lib64)
+  set(PYTHIA8_INCLUDE_DIRS ${PYTHIA8_INCLUDE_DIR} ${PYTHIA8_INCLUDE_DIR}/Pythia8 ${PYTHIA8_INCLUDE_DIR}/Pythia8Plugins )
+  set(PYTHIA8_LIBRARIES ${PYTHIA8_LIBRARY})
+  if(PYTHIA8_VERSION VERSION_LESS 8.200)
+    #Is this library needed?
+    set(PYTHIA8_LIBRARIES ${PYTHIA8_LIBRARY} ${PYTHIA8_lhapdfdummy_LIBRARY})
+  endif()
+  find_file(resHEPMC3 HepMC3.h PATHS  ${PYTHIA8_INCLUDE_DIRS} NO_DEFAULT_PATH)
+  if (resHEPMC3)
+    set(Pythia8_HEPMC3_FOUND TRUE)
+  endif()
+endif()
 
-# handle the QUIETLY and REQUIRED arguments and set PYTHIA8_FOUND to TRUE if
+# handle the QUIETLY and REQUIRED arguments and set Pythia8_FOUND to TRUE if
 # all listed variables are TRUE
+
 INCLUDE(FindPackageHandleStandardArgs)
-FIND_PACKAGE_HANDLE_STANDARD_ARGS(Pythia8 DEFAULT_MSG PYTHIA8_LIBRARIES)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(Pythia8 REQUIRED_VARS PYTHIA8_INCLUDE_DIR PYTHIA8_LIBRARIES PYTHIA8_XMLDOC_DIR VERSION_VAR PYTHIA8_VERSION HANDLE_COMPONENTS)
+
+mark_as_advanced(Pythia8_FOUND PYTHIA8_INCLUDE_DIR PYTHIA8_LIBRARY PYTHIA8_LIBRARIES PYTHIA8_XMLDOC_DIR)
 
-mark_as_advanced(PYTHIA8_FOUND PYTHIA8_LIBRARIES PYTHIA8_INCLUDES)
diff --git a/examples/extended/eventgenerator/CMakeLists.txt b/examples/extended/eventgenerator/CMakeLists.txt
index 6c700593fc9..6a685f5b2e3 100644
--- a/examples/extended/eventgenerator/CMakeLists.txt
+++ b/examples/extended/eventgenerator/CMakeLists.txt
@@ -2,6 +2,7 @@
 
 cmake_minimum_required(VERSION 3.16...3.27)
 
+set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake/Modules ${CMAKE_CURRENT_SOURCE_DIR}/../../../cmake/Modules ${CMAKE_MODULE_PATH})
 find_package(Geant4)
 include(${Geant4_USE_FILE})
 
@@ -11,26 +12,47 @@ add_subdirectory(particleGun)
 add_subdirectory(exgps)
 add_subdirectory(userPrimaryGenerator)
 
-#----------------------------------------------------------------------------
-# HepMC examples require HepMC
-#
-find_package(HepMC QUIET)
-if(HEPMC_FOUND)
-  add_subdirectory(HepMC)
-else()
-  message(STATUS "G4 Examples: HepMC package not found. --> HepMC examples disabled.") 
-endif()   
 
 #----------------------------------------------------------------------------
 # decayer6 example requires Pythia6
 #
-find_package(Pythia6 QUIET)
-if(PYTHIA6_FOUND)
+option(PYTHIA6_INTERNAL "Download and compile Pythia6" OFF)
+if (NOT PYTHIA6_INTERNAL)
+  find_package(Pythia6)
+endif()
+if(PYTHIA6_FOUND OR PYTHIA6_INTERNAL)
+  if (PYTHIA6_INTERNAL)
+    message(STATUS "Pythia6 will be downloaded and compiled")
+    include(FetchContent)
+    FetchContent_Declare(
+    p6
+    URL      https://pythia.org/download/pythia6/pythia6428-split.tgz
+    URL_HASH MD5=5391da11b95aa1d90600bc69da4f84cd
+    )
+    FetchContent_GetProperties(p6)
+    if (NOT p6_POPULATED)
+      FetchContent_Populate(p6)
+    endif()
+    file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/CMakeLists.txt.pythia6 DESTINATION ${p6_SOURCE_DIR})
+    file(COPY ${CMAKE_CURRENT_SOURCE_DIR}/pyinit.f DESTINATION ${p6_SOURCE_DIR})
+    file(RENAME ${p6_SOURCE_DIR}/CMakeLists.txt.pythia6 ${p6_SOURCE_DIR}/CMakeLists.txt)
+    add_subdirectory(${p6_SOURCE_DIR} ${p6_BINARY_DIR})
+    set(PYTHIA6_LIBRARIES G4Pythia6)
+  endif()
   add_subdirectory(pythia/decayer6)
 else()
   message(STATUS "G4 Examples: Pythia6 package not found. --> decayer6 example disabled.") 
 endif()
 
+#----------------------------------------------------------------------------
+# HepMC examples require HepMC
+#
+find_package(HepMC QUIET)
+if(HEPMC_FOUND)
+  add_subdirectory(HepMC)
+else()
+  message(STATUS "G4 Examples: HepMC package not found. --> HepMC examples disabled.") 
+endif()  
 #----------------------------------------------------------------------------
 # py8decayer example requires Pythia8
 #
diff --git a/examples/extended/eventgenerator/CMakeLists.txt.pythia6 b/examples/extended/eventgenerator/CMakeLists.txt.pythia6
index 05448b9e06d..3a74c7eb7f3 100644
--- a/examples/extended/eventgenerator/CMakeLists.txt.pythia6
+++ b/examples/extended/eventgenerator/CMakeLists.txt.pythia6
@@ -1,35 +1,28 @@
-# CMake configuration file for building Pythia6 from the source
-# downloaded from the PYTHIA6 download site:
-# http://www.hepforge.org/downloads/pythia6
-#
-# To build Pythia6 library:
-# % cd mydir
-# % mkdir pythia6_source
-# % mkdir pythia6_build
-# % mkdir pythia6
-# % cp CMakeLists.txt.pythia6 pythia6_source/CMakeLists.txt
-# % cp pythia6-version.f pythia6_source 
-# % cd pythia6_build
-# % cmake -DCMAKE_INSTALL_PREFIX=../pythia6 ../pythia6_source
-# % make
-# % make install
-
-#----------------------------------------------------------------------------
-# Setup the project
-cmake_minimum_required(VERSION 3.16...3.27)
-project(pythia6 Fortran)
-
 #----------------------------------------------------------------------------
 # Locate sources and headers for this project
 #
-file(GLOB sources ${PROJECT_SOURCE_DIR}/*.f)
 
+# file(GLOB sources ${CMAKE_CURRENT_SOURCE_DIR}/*.f)
+#AV The original line from pythia6. We do not use pdfset.f as we link with LHAPDF
+#SRCS := $(wildcard py*.f) $(wildcard struct*.f) $(wildcard up*.f) ssmssm.f sugra.f visaje.f $(wildcard fh*.f) pdfset.f
+enable_language(Fortran)
+file(GLOB py_sources ${CMAKE_CURRENT_SOURCE_DIR}/py*.f)
+file(GLOB struct_sources ${CMAKE_CURRENT_SOURCE_DIR}/struct*.f)
+file(GLOB up_sources ${CMAKE_CURRENT_SOURCE_DIR}/up*.f)
+file(GLOB fh_sources ${CMAKE_CURRENT_SOURCE_DIR}/fh*.f)
 #----------------------------------------------------------------------------
 # Add library
 #
-add_library(Pythia6 SHARED ${sources})
-
+add_library(G4Pythia6 SHARED ${py_sources} 
+                             ${struct_sources} 
+                             ${up_sources} 
+                             ${fh_sources} 
+                             ${CMAKE_CURRENT_SOURCE_DIR}/ssmssm.f 
+                             ${CMAKE_CURRENT_SOURCE_DIR}/sugra.f 
+                             ${CMAKE_CURRENT_SOURCE_DIR}/visaje.f 
+                             ${CMAKE_CURRENT_SOURCE_DIR}/pdfset.f
+                             )
 #----------------------------------------------------------------------------
 # Install library
 #
-install(TARGETS Pythia6 DESTINATION lib)
+install(TARGETS G4Pythia6 DESTINATION ${CMAKE_INSTALL_LIBDIR})
diff --git a/examples/extended/eventgenerator/HepMC/HepMCEx01/CMakeLists.txt b/examples/extended/eventgenerator/HepMC/HepMCEx01/CMakeLists.txt
index 9f0833388b7..e6b14947f28 100644
--- a/examples/extended/eventgenerator/HepMC/HepMCEx01/CMakeLists.txt
+++ b/examples/extended/eventgenerator/HepMC/HepMCEx01/CMakeLists.txt
@@ -1,7 +1,7 @@
 #----------------------------------------------------------------------------
 # Setup the project
 cmake_minimum_required(VERSION 3.16...3.27)
-project(HepMCEx01)
+project(HepMCEx01 LANGUAGES C CXX Fortran )
 
 #----------------------------------------------------------------------------
 # Find Geant4 package, activating all available UI and Vis drivers by default
@@ -24,43 +24,50 @@ include(${Geant4_USE_FILE})
 # Find HepMC (required package)
 #
 find_package(HepMC REQUIRED)
-
+#----------------------------------------------------------------------------
+# Find LHAPDF (required package)
+#
+find_package(LHAPDF REQUIRED)
 #----------------------------------------------------------------------------
 # Find Pythia6 (optional package)
 #
-find_package(Pythia6 QUIET)
-if(PYTHIA6_FOUND)
+if (NOT PYTHIA6_INTERNAL)
+  find_package(Pythia6)
+endif()
+if(PYTHIA6_FOUND OR PYTHIA6_INTERNAL)
   message(STATUS "G4 Examples: Pythia6 found. --> HepMCEx01 example with Pythia6 enabled.") 
-  add_definitions(-DG4LIB_USE_PYTHIA) 
+  add_definitions(-DG4LIB_USE_PYTHIA)
+    enable_language(Fortran)
+  set (generator_sources 
+   ${PROJECT_SOURCE_DIR}/external/initpydata.f
+   ${PROJECT_SOURCE_DIR}/external/upevnt.F
+   ${PROJECT_SOURCE_DIR}/external/upinit.F
+   ${PROJECT_SOURCE_DIR}/external/upveto.F
+   )
 else()
   set(PYTHIA6_LIBRARIES "")  
+  set (generator_sources "")
 endif()
 
 #----------------------------------------------------------------------------
 # Locate sources and headers for this project
 #
-include_directories(${PROJECT_SOURCE_DIR}/include 
-                    ${Geant4_INCLUDE_DIR}
-                    ${HEPMC_INCLUDE_DIR})
 file(GLOB sources ${PROJECT_SOURCE_DIR}/src/*.cc)
 file(GLOB headers ${PROJECT_SOURCE_DIR}/include/*.hh)
 
 #----------------------------------------------------------------------------
 # Add the executable, and link it to the Geant4 libraries
 #
-add_executable(HepMCEx01 HepMCEx01.cc ${sources} ${headers})
-#target_link_libraries(HepMCEx01 ${Geant4_LIBRARIES}
-#                      ${HEPMC_LIBRARIES} ${HEPMC_FIO_LIBRARIES}
-#                      ${PYTHIA6_LIBRARIES} gfortran)
+add_executable(HepMCEx01 HepMCEx01.cc ${sources} ${headers} ${generator_sources})
 target_link_libraries(HepMCEx01 ${Geant4_LIBRARIES}
                       ${HEPMC_LIBRARIES} ${HEPMC_FIO_LIBRARIES}
-                      ${PYTHIA6_LIBRARIES})
-
-# if pythia is compiled with g77, link with -lg2c instead.
-#target_link_libraries(HepMCEx01 ${Geant4_LIBRARIES}
-#                      ${HEPMC_LIBRARIES} ${HEPMC_FIO_LIBRARIES}
-#                      ${PYTHIA6_LIBRARIES} g2c)
-
+                      ${PYTHIA6_LIBRARIES} ${LHAPDF_LIBRARIES})
+target_include_directories(HepMCEx01 PRIVATE ${PROJECT_SOURCE_DIR}/include 
+                                             ${Geant4_INCLUDE_DIR}
+                                             ${HEPMC_INCLUDE_DIR})
+if(PYTHIA6_FOUND)
+set_target_properties(HepMCEx01 PROPERTIES LINKER_LANGUAGE Fortran)
+endif()
 #----------------------------------------------------------------------------
 # Copy all scripts to the build directory, i.e. the directory in which we
 # build HepMCEx01. This is so that we can run the executable directly because it
diff --git a/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upevnt.F b/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upevnt.F
new file mode 100644
index 00000000000..15e72907f7b
--- /dev/null
+++ b/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upevnt.F
@@ -0,0 +1,28 @@
+ 
+C*********************************************************************
+ 
+C...UPEVNT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Depending on cross section model chosen, it either has
+C...to generate a process of the type IDPRUP requested, or pick a type
+C...itself and generate this event. The event is to be stored in the
+C...HEPEUP commonblock, including (often) an event weight.
+ 
+      SUBROUTINE UPEVNT
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process event common block.
+      INTEGER MAXNUP
+      PARAMETER (MAXNUP=500)
+      INTEGER NUP,IDPRUP,IDUP,ISTUP,MOTHUP,ICOLUP
+      DOUBLE PRECISION XWGTUP,SCALUP,AQEDUP,AQCDUP,PUP,VTIMUP,SPINUP
+      COMMON/HEPEUP/NUP,IDPRUP,XWGTUP,SCALUP,AQEDUP,AQCDUP,IDUP(MAXNUP),
+     &ISTUP(MAXNUP),MOTHUP(2,MAXNUP),ICOLUP(2,MAXNUP),PUP(5,MAXNUP),
+     &VTIMUP(MAXNUP),SPINUP(MAXNUP)
+      SAVE /HEPEUP/
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upinit.F b/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upinit.F
new file mode 100644
index 00000000000..6492b62b09c
--- /dev/null
+++ b/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upinit.F
@@ -0,0 +1,26 @@
+ 
+C*********************************************************************
+ 
+C...UPINIT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Is supposed to fill the HEPRUP commonblock with info
+C...on incoming beams and allowed processes.
+ 
+      SUBROUTINE UPINIT
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process initialization commonblock.
+      INTEGER MAXPUP
+      PARAMETER (MAXPUP=100)
+      INTEGER IDBMUP,PDFGUP,PDFSUP,IDWTUP,NPRUP,LPRUP
+      DOUBLE PRECISION EBMUP,XSECUP,XERRUP,XMAXUP
+      COMMON/HEPRUP/IDBMUP(2),EBMUP(2),PDFGUP(2),PDFSUP(2),
+     &IDWTUP,NPRUP,XSECUP(MAXPUP),XERRUP(MAXPUP),XMAXUP(MAXPUP),
+     &LPRUP(MAXPUP)
+      SAVE /HEPRUP/
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upveto.F b/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upveto.F
new file mode 100644
index 00000000000..48af84ee02e
--- /dev/null
+++ b/examples/extended/eventgenerator/HepMC/HepMCEx01/external/upveto.F
@@ -0,0 +1,28 @@
+ 
+C*********************************************************************
+ 
+C...UPEVNT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Depending on cross section model chosen, it either has
+C...to generate a process of the type IDPRUP requested, or pick a type
+C...itself and generate this event. The event is to be stored in the
+C...HEPEUP commonblock, including (often) an event weight.
+ 
+      SUBROUTINE UPVETO
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process event common block.
+      INTEGER MAXNUP
+      PARAMETER (MAXNUP=500)
+      INTEGER NUP,IDPRUP,IDUP,ISTUP,MOTHUP,ICOLUP
+      DOUBLE PRECISION XWGTUP,SCALUP,AQEDUP,AQCDUP,PUP,VTIMUP,SPINUP
+      COMMON/HEPEUP/NUP,IDPRUP,XWGTUP,SCALUP,AQEDUP,AQCDUP,IDUP(MAXNUP),
+     &ISTUP(MAXNUP),MOTHUP(2,MAXNUP),ICOLUP(2,MAXNUP),PUP(5,MAXNUP),
+     &VTIMUP(MAXNUP),SPINUP(MAXNUP)
+      SAVE /HEPEUP/
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/HepMC/HepMCEx02/CMakeLists.txt b/examples/extended/eventgenerator/HepMC/HepMCEx02/CMakeLists.txt
index 47acb01460b..b9df081ff7d 100644
--- a/examples/extended/eventgenerator/HepMC/HepMCEx02/CMakeLists.txt
+++ b/examples/extended/eventgenerator/HepMC/HepMCEx02/CMakeLists.txt
@@ -1,7 +1,7 @@
 #----------------------------------------------------------------------------
 # Setup the project
 cmake_minimum_required(VERSION 3.16...3.27)
-project(HepMCEx02)
+project(HepMCEx02 LANGUAGES C CXX Fortran )
 
 #----------------------------------------------------------------------------
 # Find Geant4 package, activating all available UI and Vis drivers by default
@@ -24,42 +24,50 @@ include(${Geant4_USE_FILE})
 # Find HepMC (required package)
 #
 find_package(HepMC REQUIRED)
+#----------------------------------------------------------------------------
+# Find LHAPDF (required package)
+#
+find_package(LHAPDF REQUIRED)
 
 #----------------------------------------------------------------------------
 # Find Pythia6 (optional package)
 #
-find_package(Pythia6 QUIET)
-if(PYTHIA6_FOUND)
+if (NOT PYTHIA6_INTERNAL)
+  find_package(Pythia6)
+endif()
+if(PYTHIA6_FOUND OR PYTHIA6_INTERNAL)
   message(STATUS "G4 Examples: Pythia6 found. --> HepMCEx02 example with Pythia6 enabled.") 
-  add_definitions(-DG4LIB_USE_PYTHIA) 
+  add_definitions(-DG4LIB_USE_PYTHIA)
+  enable_language(Fortran)
+  set (generator_sources 
+   ${PROJECT_SOURCE_DIR}/external/upevnt.F
+   ${PROJECT_SOURCE_DIR}/external/upinit.F
+   ${PROJECT_SOURCE_DIR}/external/upveto.F
+   )
 else()
   set(PYTHIA6_LIBRARIES "")  
+  set (generator_sources "")
 endif()
 
 #----------------------------------------------------------------------------
 # Locate sources and headers for this project
 #
-include_directories(${PROJECT_SOURCE_DIR}/include 
-                    ${Geant4_INCLUDE_DIR}
-                    ${HEPMC_INCLUDE_DIR})
 file(GLOB sources ${PROJECT_SOURCE_DIR}/src/*.cc)
 file(GLOB headers ${PROJECT_SOURCE_DIR}/include/*.hh)
 
 #----------------------------------------------------------------------------
 # Add the executable, and link it to the Geant4 libraries
 #
-add_executable(HepMCEx02 HepMCEx02.cc ${sources} ${headers})
-#target_link_libraries(HepMCEx02 ${Geant4_LIBRARIES}
-#                      ${HEPMC_LIBRARIES} ${HEPMC_FIO_LIBRARIES}
-#                      ${PYTHIA6_LIBRARIES} gfortran)
+add_executable(HepMCEx02 HepMCEx02.cc ${sources} ${headers} ${generator_sources})
 target_link_libraries(HepMCEx02 ${Geant4_LIBRARIES}
                       ${HEPMC_LIBRARIES} ${HEPMC_FIO_LIBRARIES}
-                      ${PYTHIA6_LIBRARIES})
-
-# if pythia is compiled with g77, link with -lg2c instead.
-#target_link_libraries(HepMCEx02 ${Geant4_LIBRARIES}
-#                      ${HEPMC_LIBRARIES} ${HEPMC_FIO_LIBRARIES}
-#                      ${PYTHIA6_LIBRARIES} g2c)
+                      ${PYTHIA6_LIBRARIES} ${LHAPDF_LIBRARIES})
+target_include_directories(HepMCEx02 PRIVATE ${PROJECT_SOURCE_DIR}/include 
+                                             ${Geant4_INCLUDE_DIR}
+                                             ${HEPMC_INCLUDE_DIR})
+if(PYTHIA6_FOUND)
+  set_target_properties(HepMCEx02 PROPERTIES LINKER_LANGUAGE Fortran)
+endif()
 
 #----------------------------------------------------------------------------
 # Copy all scripts to the build directory, i.e. the directory in which we
diff --git a/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upevnt.F b/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upevnt.F
new file mode 100644
index 00000000000..15e72907f7b
--- /dev/null
+++ b/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upevnt.F
@@ -0,0 +1,28 @@
+ 
+C*********************************************************************
+ 
+C...UPEVNT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Depending on cross section model chosen, it either has
+C...to generate a process of the type IDPRUP requested, or pick a type
+C...itself and generate this event. The event is to be stored in the
+C...HEPEUP commonblock, including (often) an event weight.
+ 
+      SUBROUTINE UPEVNT
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process event common block.
+      INTEGER MAXNUP
+      PARAMETER (MAXNUP=500)
+      INTEGER NUP,IDPRUP,IDUP,ISTUP,MOTHUP,ICOLUP
+      DOUBLE PRECISION XWGTUP,SCALUP,AQEDUP,AQCDUP,PUP,VTIMUP,SPINUP
+      COMMON/HEPEUP/NUP,IDPRUP,XWGTUP,SCALUP,AQEDUP,AQCDUP,IDUP(MAXNUP),
+     &ISTUP(MAXNUP),MOTHUP(2,MAXNUP),ICOLUP(2,MAXNUP),PUP(5,MAXNUP),
+     &VTIMUP(MAXNUP),SPINUP(MAXNUP)
+      SAVE /HEPEUP/
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upinit.F b/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upinit.F
new file mode 100644
index 00000000000..6492b62b09c
--- /dev/null
+++ b/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upinit.F
@@ -0,0 +1,26 @@
+ 
+C*********************************************************************
+ 
+C...UPINIT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Is supposed to fill the HEPRUP commonblock with info
+C...on incoming beams and allowed processes.
+ 
+      SUBROUTINE UPINIT
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process initialization commonblock.
+      INTEGER MAXPUP
+      PARAMETER (MAXPUP=100)
+      INTEGER IDBMUP,PDFGUP,PDFSUP,IDWTUP,NPRUP,LPRUP
+      DOUBLE PRECISION EBMUP,XSECUP,XERRUP,XMAXUP
+      COMMON/HEPRUP/IDBMUP(2),EBMUP(2),PDFGUP(2),PDFSUP(2),
+     &IDWTUP,NPRUP,XSECUP(MAXPUP),XERRUP(MAXPUP),XMAXUP(MAXPUP),
+     &LPRUP(MAXPUP)
+      SAVE /HEPRUP/
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upveto.F b/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upveto.F
new file mode 100644
index 00000000000..48af84ee02e
--- /dev/null
+++ b/examples/extended/eventgenerator/HepMC/HepMCEx02/external/upveto.F
@@ -0,0 +1,28 @@
+ 
+C*********************************************************************
+ 
+C...UPEVNT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Depending on cross section model chosen, it either has
+C...to generate a process of the type IDPRUP requested, or pick a type
+C...itself and generate this event. The event is to be stored in the
+C...HEPEUP commonblock, including (often) an event weight.
+ 
+      SUBROUTINE UPVETO
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process event common block.
+      INTEGER MAXNUP
+      PARAMETER (MAXNUP=500)
+      INTEGER NUP,IDPRUP,IDUP,ISTUP,MOTHUP,ICOLUP
+      DOUBLE PRECISION XWGTUP,SCALUP,AQEDUP,AQCDUP,PUP,VTIMUP,SPINUP
+      COMMON/HEPEUP/NUP,IDPRUP,XWGTUP,SCALUP,AQEDUP,AQCDUP,IDUP(MAXNUP),
+     &ISTUP(MAXNUP),MOTHUP(2,MAXNUP),ICOLUP(2,MAXNUP),PUP(5,MAXNUP),
+     &VTIMUP(MAXNUP),SPINUP(MAXNUP)
+      SAVE /HEPEUP/
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/pyinit.f b/examples/extended/eventgenerator/pyinit.f
new file mode 100644
index 00000000000..7b8c2b57a4c
--- /dev/null
+++ b/examples/extended/eventgenerator/pyinit.f
@@ -0,0 +1,315 @@
+ 
+C*********************************************************************
+ 
+C...PYINIT
+C...Initializes the generation procedure; finds maxima of the
+C...differential cross-sections to be used for weighting.
+      SUBROUTINE PYINIT(FRAME,BEAM,TARGET,WIN)
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+      INTEGER PYK,PYCHGE,PYCOMP
+C...Commonblocks.
+      COMMON/PYDAT1/MSTU(200),PARU(200),MSTJ(200),PARJ(200)
+      COMMON/PYDAT2/KCHG(500,4),PMAS(500,4),PARF(2000),VCKM(4,4)
+      COMMON/PYDAT3/MDCY(500,3),MDME(8000,2),BRAT(8000),KFDP(8000,5)
+      COMMON/PYDAT4/CHAF(500,2)
+      CHARACTER CHAF*16
+      COMMON/PYSUBS/MSEL,MSELPD,MSUB(500),KFIN(2,-40:40),CKIN(200)
+      COMMON/PYPARS/MSTP(200),PARP(200),MSTI(200),PARI(200)
+      COMMON/PYINT1/MINT(400),VINT(400)
+      COMMON/PYINT2/ISET(500),KFPR(500,2),COEF(500,20),ICOL(40,4,2)
+      COMMON/PYINT5/NGENPD,NGEN(0:500,3),XSEC(0:500,3)
+      COMMON/PYPUED/IUED(0:99),RUED(0:99)
+      SAVE /PYDAT1/,/PYDAT2/,/PYDAT3/,/PYDAT4/,/PYSUBS/,/PYPARS/,
+     &/PYINT1/,/PYINT2/,/PYINT5/,/PYPUED/
+C...Local arrays and character variables.
+      DIMENSION ALAMIN(20),NFIN(20)
+      CHARACTER*(*) FRAME,BEAM,TARGET
+      CHARACTER CHFRAM*12,CHBEAM*12,CHTARG*12,CHLH(2)*6
+ 
+C...Interface to PDFLIB.
+      COMMON/W50511/NPTYPE,NGROUP,NSET,MODE,NFL,LO,TMAS
+      COMMON/W50512/QCDL4,QCDL5
+      SAVE /W50511/,/W50512/
+      DOUBLE PRECISION VALUE(20),TMAS,QCDL4,QCDL5
+      CHARACTER*20 PARM(20)
+      DATA VALUE/20*0D0/,PARM/20*' '/
+ 
+C...Data:Lambda and n_f values for parton distributions..
+      DATA ALAMIN/0.177D0,0.239D0,0.247D0,0.2322D0,0.248D0,0.248D0,
+     &0.192D0,0.326D0,2*0.2D0,0.2D0,0.2D0,0.29D0,0.2D0,0.4D0,5*0.2D0/,
+     &NFIN/20*4/
+      DATA CHLH/'lepton','hadron'/
+C...Check that BLOCK DATA PYDATA has been loaded.
+      CALL PYCKBD
+ 
+C...Reset MINT and VINT arrays. Write headers.
+      MSTI(53)=0
+      DO 100 J=1,400
+        MINT(J)=0
+        VINT(J)=0D0
+  100 CONTINUE
+      IF(MSTU(12).NE.12345) CALL PYLIST(0)
+      IF(MSTP(122).GE.1) WRITE(MSTU(11),5100)
+ 
+ 
+C...Reset error counters.
+      MSTU(23)=0
+      MSTU(27)=0
+      MSTU(30)=0
+ 
+ 
+C...Reset processes that should not be on.
+      MSUB(96)=0
+      MSUB(97)=0
+C...Select global FSR/ISR/UE parameter set = 'tune' 
+C...See routine PYTUNE for details
+      IF (MSTP(5).NE.0) THEN
+        MSTP5=MSTP(5)
+        CALL PYTUNE(MSTP5)
+      ENDIF
+
+C...Call user process initialization routine.
+      IF(FRAME(1:1).EQ.'u'.OR.FRAME(1:1).EQ.'U') THEN
+        MSEL=0
+        CALL UPINIT
+        MSEL=0
+      ENDIF
+ 
+C...Maximum 4 generations; set maximum number of allowed flavours.
+      MSTP(1)=MIN(4,MSTP(1))
+      MSTU(114)=MIN(MSTU(114),2*MSTP(1))
+      MSTP(58)=MIN(MSTP(58),2*MSTP(1))
+ 
+C...Sum up Cabibbo-Kobayashi-Maskawa factors for each quark/lepton.
+      DO 120 I=-20,20
+        VINT(180+I)=0D0
+        IA=IABS(I)
+        IF(IA.GE.1.AND.IA.LE.2*MSTP(1)) THEN
+          DO 110 J=1,MSTP(1)
+            IB=2*J-1+MOD(IA,2)
+            IF(IB.GE.6.AND.MSTP(9).EQ.0) GOTO 110
+            IPM=(5-ISIGN(1,I))/2
+            IDC=J+MDCY(IA,2)+2
+            IF(MDME(IDC,1).EQ.1.OR.MDME(IDC,1).EQ.IPM) VINT(180+I)=
+     &      VINT(180+I)+VCKM((IA+1)/2,(IB+1)/2)
+  110     CONTINUE
+        ELSEIF(IA.GE.11.AND.IA.LE.10+2*MSTP(1)) THEN
+          VINT(180+I)=1D0
+        ENDIF
+  120 CONTINUE
+C...Initialize parton distributions: PDFLIB.
+      IF(MSTP(52).EQ.2) THEN
+        PARM(1)='NPTYPE'
+        VALUE(1)=1
+        PARM(2)='NGROUP'
+        VALUE(2)=MSTP(51)/1000
+        PARM(3)='NSET'
+        VALUE(3)=MOD(MSTP(51),1000)
+        PARM(4)='TMAS'
+        VALUE(4)=PMAS(6,1)
+        CALL PDFSET(PARM,VALUE)
+        MINT(93)=1000000+MSTP(51)
+      ENDIF
+C...Choose Lambda value to use in alpha-strong.
+      MSTU(111)=MSTP(2)
+      IF(MSTP(3).GE.2) THEN
+        ALAM=0.2D0
+        NF=4
+        IF(MSTP(52).EQ.1.AND.MSTP(51).GE.1.AND.MSTP(51).LE.20) THEN
+          ALAM=ALAMIN(MSTP(51))
+          NF=NFIN(MSTP(51))
+        ELSEIF(MSTP(52).EQ.2.AND.NFL.EQ.5) THEN
+          ALAM=QCDL5
+          NF=5
+        ELSEIF(MSTP(52).EQ.2) THEN
+          ALAM=QCDL4
+          NF=4
+        ENDIF
+        PARP(1)=ALAM
+        PARP(61)=ALAM
+        PARP(72)=ALAM
+        PARU(112)=ALAM
+        MSTU(112)=NF
+        IF(MSTP(3).EQ.3) PARJ(81)=ALAM
+      ENDIF
+ 
+C...Initialize the UED masses and widths
+      IF (IUED(1).EQ.1) CALL PYXDIN
+C...Initialize the SUSY generation: couplings, masses,
+C...decay modes, branching ratios, and so on.
+      CALL PYMSIN
+C...Initialize widths and partial widths for resonances.
+      CALL PYINRE
+C...Set Z0 mass and width for e+e- routines.
+      PARJ(123)=PMAS(23,1)
+      PARJ(124)=PMAS(23,2)
+C...Identify beam and target particles and frame of process.
+      CHFRAM=FRAME(1:len(FRAME))//' '
+      CHBEAM=BEAM(1:len(BEAM))//' '
+      CHTARG=TARGET(1:len(TARGET))//' '
+      CALL PYINBM(CHFRAM,CHBEAM,CHTARG,WIN)
+      IF(MINT(65).EQ.1) GOTO 170
+C...For gamma-p or gamma-gamma allow many (3 or 6) alternatives.
+C...For e-gamma allow 2 alternatives.
+      MINT(121)=1
+      IF(MSTP(14).EQ.10.AND.(MSEL.EQ.1.OR.MSEL.EQ.2)) THEN
+        IF((MINT(11).EQ.22.OR.MINT(12).EQ.22).AND.
+     &  (IABS(MINT(11)).GT.100.OR.IABS(MINT(12)).GT.100)) MINT(121)=3
+        IF(MINT(11).EQ.22.AND.MINT(12).EQ.22) MINT(121)=6
+        IF((MINT(11).EQ.22.OR.MINT(12).EQ.22).AND.
+     &  (IABS(MINT(11)).EQ.11.OR.IABS(MINT(12)).EQ.11)) MINT(121)=2
+      ELSEIF(MSTP(14).EQ.20.AND.(MSEL.EQ.1.OR.MSEL.EQ.2)) THEN
+        IF((MINT(11).EQ.22.OR.MINT(12).EQ.22).AND.
+     &  (IABS(MINT(11)).GT.100.OR.IABS(MINT(12)).GT.100)) MINT(121)=3
+        IF(MINT(11).EQ.22.AND.MINT(12).EQ.22) MINT(121)=9
+      ELSEIF(MSTP(14).EQ.25.AND.(MSEL.EQ.1.OR.MSEL.EQ.2)) THEN
+        IF((MINT(11).EQ.22.OR.MINT(12).EQ.22).AND.
+     &  (IABS(MINT(11)).GT.100.OR.IABS(MINT(12)).GT.100)) MINT(121)=2
+        IF(MINT(11).EQ.22.AND.MINT(12).EQ.22) MINT(121)=4
+      ELSEIF(MSTP(14).EQ.30.AND.(MSEL.EQ.1.OR.MSEL.EQ.2)) THEN
+        IF((MINT(11).EQ.22.OR.MINT(12).EQ.22).AND.
+     &  (IABS(MINT(11)).GT.100.OR.IABS(MINT(12)).GT.100)) MINT(121)=4
+        IF(MINT(11).EQ.22.AND.MINT(12).EQ.22) MINT(121)=13
+      ENDIF
+      MINT(123)=MSTP(14)
+      IF((MSTP(14).EQ.10.OR.MSTP(14).EQ.20.OR.MSTP(14).EQ.25.OR.
+     &MSTP(14).EQ.30).AND.MSEL.NE.1.AND.MSEL.NE.2) MINT(123)=0
+      IF(MSTP(14).GE.11.AND.MSTP(14).LE.19) THEN
+        IF(MSTP(14).EQ.11) MINT(123)=0
+        IF(MSTP(14).EQ.12.OR.MSTP(14).EQ.14) MINT(123)=5
+        IF(MSTP(14).EQ.13.OR.MSTP(14).EQ.17) MINT(123)=6
+        IF(MSTP(14).EQ.15) MINT(123)=2
+        IF(MSTP(14).EQ.16.OR.MSTP(14).EQ.18) MINT(123)=7
+        IF(MSTP(14).EQ.19) MINT(123)=3
+      ELSEIF(MSTP(14).GE.21.AND.MSTP(14).LE.24) THEN
+        IF(MSTP(14).EQ.21) MINT(123)=0
+        IF(MSTP(14).EQ.22.OR.MSTP(14).EQ.23) MINT(123)=4
+        IF(MSTP(14).EQ.24) MINT(123)=1
+      ELSEIF(MSTP(14).GE.26.AND.MSTP(14).LE.29) THEN
+        IF(MSTP(14).EQ.26.OR.MSTP(14).EQ.28) MINT(123)=8
+        IF(MSTP(14).EQ.27.OR.MSTP(14).EQ.29) MINT(123)=9
+      ENDIF
+C...Set up kinematics of process.
+      CALL PYINKI(0)
+ 
+C...Set up kinematics for photons inside leptons.
+      IF(MINT(141).NE.0.OR.MINT(142).NE.0) CALL PYGAGA(1,WTGAGA)
+ 
+C...Precalculate flavour selection weights.
+      CALL PYKFIN
+C...Loop over gamma-p or gamma-gamma alternatives.
+      CKIN3=CKIN(3)
+      MSAV48=0
+      DO 160 IGA=1,MINT(121)
+        CKIN(3)=CKIN3
+        MINT(122)=IGA
+ 
+C...Select partonic subprocesses to be included in the simulation.
+        CALL PYINPR
+        MINT(101)=1
+        MINT(102)=1
+        MINT(103)=MINT(11)
+        MINT(104)=MINT(12)
+ 
+C...Count number of subprocesses on.
+        MINT(48)=0
+        DO 130 ISUB=1,500
+          IF(MINT(50).EQ.0.AND.ISUB.GE.91.AND.ISUB.LE.96.AND.
+     &    MSUB(ISUB).EQ.1.AND.MINT(121).GT.1) THEN
+            MSUB(ISUB)=0
+          ELSEIF(MINT(50).EQ.0.AND.ISUB.GE.91.AND.ISUB.LE.96.AND.
+     &    MSUB(ISUB).EQ.1) THEN
+            WRITE(MSTU(11),5200) ISUB,CHLH(MINT(41)),CHLH(MINT(42))
+            CALL PYSTOP(1)
+          ELSEIF(MSUB(ISUB).EQ.1.AND.ISET(ISUB).EQ.-1) THEN
+            WRITE(MSTU(11),5300) ISUB
+            CALL PYSTOP(1)
+          ELSEIF(MSUB(ISUB).EQ.1.AND.ISET(ISUB).LE.-2) THEN
+            WRITE(MSTU(11),5400) ISUB
+            CALL PYSTOP(1)
+          ELSEIF(MSUB(ISUB).EQ.1) THEN
+            MINT(48)=MINT(48)+1
+          ENDIF
+  130   CONTINUE
+ 
+C...Stop or raise warning flag if no subprocesses on.
+        IF(MINT(121).EQ.1.AND.MINT(48).EQ.0) THEN
+          IF(MSTP(127).NE.1) THEN
+            WRITE(MSTU(11),5500)
+            CALL PYSTOP(1)
+          ELSE
+            WRITE(MSTU(11),5700)
+            MSTI(53)=1
+          ENDIF
+        ENDIF
+        MINT(49)=MINT(48)-MSUB(91)-MSUB(92)-MSUB(93)-MSUB(94)
+        MSAV48=MSAV48+MINT(48)
+ 
+C...Reset variables for cross-section calculation.
+        DO 150 I=0,500
+          DO 140 J=1,3
+            NGEN(I,J)=0
+            XSEC(I,J)=0D0
+  140     CONTINUE
+  150   CONTINUE
+ 
+C...Find parametrized total cross-sections.
+        CALL PYXTOT
+        VINT(318)=VINT(317)
+ 
+C...Maxima of differential cross-sections.
+        IF(MSTP(121).LE.1) CALL PYMAXI
+ 
+C...Initialize possibility of pileup events.
+        IF(MINT(121).GT.1) MSTP(131)=0
+        IF(MSTP(131).NE.0) CALL PYPILE(1)
+ 
+C...Initialize multiple interactions with variable impact parameter.
+        IF(MINT(50).EQ.1) THEN
+          PTMN=PARP(82)*(VINT(1)/PARP(89))**PARP(90)
+          IF(MOD(MSTP(81),10).EQ.0.AND.(CKIN(3).GT.PTMN.OR.
+     &    ((MSEL.NE.1.AND.MSEL.NE.2)))) MSTP(82)=MIN(1,MSTP(82))
+          IF((MINT(49).NE.0.OR.MSTP(131).NE.0).AND.MSTP(82).GE.2) THEN
+            MINT(35)=1
+            CALL PYMULT(1)
+            MINT(35)=3
+            CALL PYMIGN(1)
+          ENDIF
+        ENDIF
+ 
+C...Save results for gamma-p and gamma-gamma alternatives.
+        IF(MINT(121).GT.1) CALL PYSAVE(1,IGA)
+  160 CONTINUE
+ 
+C...Initialization finished.
+      IF(MSAV48.EQ.0) THEN
+        IF(MSTP(127).NE.1) THEN
+          WRITE(MSTU(11),5500)
+          CALL PYSTOP(1)
+        ELSE
+          WRITE(MSTU(11),5700)
+          MSTI(53)=1
+        ENDIF
+      ENDIF
+  170 IF(MSTP(122).GE.1) WRITE(MSTU(11),5600)
+ 
+C...Formats for initialization information.
+ 5100 FORMAT('1',18('*'),1X,'PYINIT: initialization of PYTHIA ',
+     &'routines',1X,17('*'))
+ 5200 FORMAT(1X,'Error: process number ',I3,' not meaningful for ',A6,
+     &'-',A6,' interactions.'/1X,'Execution stopped!')
+ 5300 FORMAT(1X,'Error: requested subprocess',I4,' not implemented.'/
+     &1X,'Execution stopped!')
+ 5400 FORMAT(1X,'Error: requested subprocess',I4,' not existing.'/
+     &1X,'Execution stopped!')
+ 5500 FORMAT(1X,'Error: no subprocess switched on.'/
+     &1X,'Execution stopped.')
+ 5600 FORMAT(/1X,22('*'),1X,'PYINIT: initialization completed',1X,
+     &22('*'))
+ 5700 FORMAT(1X,'Error: no subprocess switched on.'/
+     &1X,'Execution will stop if you try to generate events.')
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/pythia/decayer6/CMakeLists.txt b/examples/extended/eventgenerator/pythia/decayer6/CMakeLists.txt
index 00fb0f84ecd..37d7bf39484 100644
--- a/examples/extended/eventgenerator/pythia/decayer6/CMakeLists.txt
+++ b/examples/extended/eventgenerator/pythia/decayer6/CMakeLists.txt
@@ -1,7 +1,7 @@
 #----------------------------------------------------------------------------
 # Setup the project
 cmake_minimum_required(VERSION 3.16...3.27)
-project(decayer6)
+project(decayer6 LANGUAGES C CXX Fortran )
 
 #----------------------------------------------------------------------------
 # Find Geant4 package, activating all available UI and Vis drivers by default
@@ -23,18 +23,23 @@ include(${Geant4_USE_FILE})
 #----------------------------------------------------------------------------
 # Find Pythia6 (required package)
 #
-find_package(Pythia6 REQUIRED)
-
+if (NOT PYTHIA6_INTERNAL)
+  find_package(Pythia6 REQUIRED)
+endif()
+#----------------------------------------------------------------------------
+# Find LHAPDF (required package)
+#
+find_package(LHAPDF REQUIRED)
 #----------------------------------------------------------------------------
 # Locate sources and headers for this project
 #
-include_directories(${PROJECT_SOURCE_DIR}/include 
-                    ${PROJECT_SOURCE_DIR}/common/include 
-                    ${Geant4_INCLUDE_DIR}
-                    ${PYTHIA6_INCLUDE_DIR})
 file(GLOB sources ${PROJECT_SOURCE_DIR}/src/*.cc ${PROJECT_SOURCE_DIR}/src/*.c)
 file(GLOB headers ${PROJECT_SOURCE_DIR}/include/*.hh)
-
+set (generator_sources 
+   ${PROJECT_SOURCE_DIR}/src/upevnt.F
+   ${PROJECT_SOURCE_DIR}/src/upinit.F
+   ${PROJECT_SOURCE_DIR}/src/upveto.F
+   )
 #----------------------------------------------------------------------------
 # Add common subdirectory and
 # - disable building examples in common
@@ -47,9 +52,17 @@ add_subdirectory(common)
 #----------------------------------------------------------------------------
 # Add the executable, and link it to the Geant4 libraries
 #
-add_executable(pythia6_decayer pythia6_decayer.cc ${sources} ${headers})
-target_link_libraries(pythia6_decayer ${common_prefix}common ${Geant4_LIBRARIES} ${PYTHIA6_LIBRARIES} )
-
+add_executable(pythia6_decayer pythia6_decayer.cc ${sources} ${headers} ${generator_sources})
+target_link_libraries(pythia6_decayer ${common_prefix}common 
+                                      ${Geant4_LIBRARIES} 
+                                      ${PYTHIA6_LIBRARIES} 
+                                      ${LHAPDF_LIBRARIES})
+target_include_directories(pythia6_decayer PRIVATE ${PROJECT_SOURCE_DIR}/include 
+                    ${PROJECT_SOURCE_DIR}/common/include 
+                    ${Geant4_INCLUDE_DIR}
+                    ${LHAPDF_INCLUDE_DIR}
+                    )
+set_target_properties(pythia6_decayer PROPERTIES LINKER_LANGUAGE Fortran)
 #----------------------------------------------------------------------------
 # Copy all scripts to the build directory, i.e. the directory in which we
 # build decayer6. This is so that we can run the executable directly because it
diff --git a/examples/extended/eventgenerator/pythia/decayer6/src/upevnt.F b/examples/extended/eventgenerator/pythia/decayer6/src/upevnt.F
new file mode 100644
index 00000000000..15e72907f7b
--- /dev/null
+++ b/examples/extended/eventgenerator/pythia/decayer6/src/upevnt.F
@@ -0,0 +1,28 @@
+ 
+C*********************************************************************
+ 
+C...UPEVNT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Depending on cross section model chosen, it either has
+C...to generate a process of the type IDPRUP requested, or pick a type
+C...itself and generate this event. The event is to be stored in the
+C...HEPEUP commonblock, including (often) an event weight.
+ 
+      SUBROUTINE UPEVNT
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process event common block.
+      INTEGER MAXNUP
+      PARAMETER (MAXNUP=500)
+      INTEGER NUP,IDPRUP,IDUP,ISTUP,MOTHUP,ICOLUP
+      DOUBLE PRECISION XWGTUP,SCALUP,AQEDUP,AQCDUP,PUP,VTIMUP,SPINUP
+      COMMON/HEPEUP/NUP,IDPRUP,XWGTUP,SCALUP,AQEDUP,AQCDUP,IDUP(MAXNUP),
+     &ISTUP(MAXNUP),MOTHUP(2,MAXNUP),ICOLUP(2,MAXNUP),PUP(5,MAXNUP),
+     &VTIMUP(MAXNUP),SPINUP(MAXNUP)
+      SAVE /HEPEUP/
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/pythia/decayer6/src/upinit.F b/examples/extended/eventgenerator/pythia/decayer6/src/upinit.F
new file mode 100644
index 00000000000..6492b62b09c
--- /dev/null
+++ b/examples/extended/eventgenerator/pythia/decayer6/src/upinit.F
@@ -0,0 +1,26 @@
+ 
+C*********************************************************************
+ 
+C...UPINIT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Is supposed to fill the HEPRUP commonblock with info
+C...on incoming beams and allowed processes.
+ 
+      SUBROUTINE UPINIT
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process initialization commonblock.
+      INTEGER MAXPUP
+      PARAMETER (MAXPUP=100)
+      INTEGER IDBMUP,PDFGUP,PDFSUP,IDWTUP,NPRUP,LPRUP
+      DOUBLE PRECISION EBMUP,XSECUP,XERRUP,XMAXUP
+      COMMON/HEPRUP/IDBMUP(2),EBMUP(2),PDFGUP(2),PDFSUP(2),
+     &IDWTUP,NPRUP,XSECUP(MAXPUP),XERRUP(MAXPUP),XMAXUP(MAXPUP),
+     &LPRUP(MAXPUP)
+      SAVE /HEPRUP/
+ 
+      RETURN
+      END
diff --git a/examples/extended/eventgenerator/pythia/decayer6/src/upveto.F b/examples/extended/eventgenerator/pythia/decayer6/src/upveto.F
new file mode 100644
index 00000000000..48af84ee02e
--- /dev/null
+++ b/examples/extended/eventgenerator/pythia/decayer6/src/upveto.F
@@ -0,0 +1,28 @@
+ 
+C*********************************************************************
+ 
+C...UPEVNT
+C...Dummy routine, to be replaced by a user implementing external
+C...processes. Depending on cross section model chosen, it either has
+C...to generate a process of the type IDPRUP requested, or pick a type
+C...itself and generate this event. The event is to be stored in the
+C...HEPEUP commonblock, including (often) an event weight.
+ 
+      SUBROUTINE UPVETO
+ 
+C...Double precision and integer declarations.
+      IMPLICIT DOUBLE PRECISION(A-H, O-Z)
+      IMPLICIT INTEGER(I-N)
+ 
+C...User process event common block.
+      INTEGER MAXNUP
+      PARAMETER (MAXNUP=500)
+      INTEGER NUP,IDPRUP,IDUP,ISTUP,MOTHUP,ICOLUP
+      DOUBLE PRECISION XWGTUP,SCALUP,AQEDUP,AQCDUP,PUP,VTIMUP,SPINUP
+      COMMON/HEPEUP/NUP,IDPRUP,XWGTUP,SCALUP,AQEDUP,AQCDUP,IDUP(MAXNUP),
+     &ISTUP(MAXNUP),MOTHUP(2,MAXNUP),ICOLUP(2,MAXNUP),PUP(5,MAXNUP),
+     &VTIMUP(MAXNUP),SPINUP(MAXNUP)
+      SAVE /HEPEUP/
+ 
+      RETURN
+      END