diff --git a/Framework/CMakeLists.txt b/Framework/CMakeLists.txt
index fe0306b6dc98d20734dea40df4d2b182a1915cbd..f5d3823c8dee6738710da7785bbaeda6688b29f0 100644
--- a/Framework/CMakeLists.txt
+++ b/Framework/CMakeLists.txt
@@ -212,8 +212,13 @@ foreach(_bundle ${BUNDLES})
 
     # Also ship mingw libraries for Inelastic fortran code. We need to do a
     # better job here and build things
-    file(GLOB MINGW_DLLS "${THIRD_PARTY_DIR}/bin/mingw/*.dll")
-    install(FILES ${MINGW_DLLS} DESTINATION ${_bundle}scripts/Inelastic)
+    if(WITH_PYTHON3)
+      install(FILES "${THIRD_PARTY_DIR}/bin/libquadmath-0.dll" "${THIRD_PARTY_DIR}/bin/libgcc_s_seh-1/*.dll"
+              DESTINATION ${_bundle}scripts/Inelastic)
+    else()
+      file(GLOB MINGW_DLLS "${THIRD_PARTY_DIR}/bin/mingw/*.dll")
+      install(FILES ${MINGW_DLLS} DESTINATION ${_bundle}scripts/Inelastic)
+    endif()
   else()
     install(DIRECTORY ../scripts/
             DESTINATION ${_bundle}scripts
diff --git a/Framework/Kernel/inc/MantidKernel/PropertyWithValueJSON.h b/Framework/Kernel/inc/MantidKernel/PropertyWithValueJSON.h
index 4982aab0b2e50ddf34105d45706153100e3c14b8..bb33edc4ece29e7d35a6f608d8944a4d3be8ef51 100644
--- a/Framework/Kernel/inc/MantidKernel/PropertyWithValueJSON.h
+++ b/Framework/Kernel/inc/MantidKernel/PropertyWithValueJSON.h
@@ -38,11 +38,11 @@ template <> struct ToCpp<int> {
 };
 /// Specialization of ToCpp for long long
 template <> struct ToCpp<long long> {
-  long operator()(const Json::Value &value) { return value.asInt64(); }
+  long long operator()(const Json::Value &value) { return value.asInt64(); }
 };
 /// Specialization of ToCpp for long
 template <> struct ToCpp<long> {
-  Json::Int64 operator()(const Json::Value &value) { return value.asInt64(); }
+  long operator()(const Json::Value &value) { return value.asInt(); }
 };
 /// Specialization of ToCpp for unsigned int
 template <> struct ToCpp<unsigned int> {
diff --git a/buildconfig/CMake/Bootstrap.cmake b/buildconfig/CMake/Bootstrap.cmake
index 5b89f874c7b5b4cd63a3c334169be5ad38bfbb5c..d8c80ef345f19c54eddb1a823dcdb0d1c0f159c1 100644
--- a/buildconfig/CMake/Bootstrap.cmake
+++ b/buildconfig/CMake/Bootstrap.cmake
@@ -10,7 +10,7 @@ if( MSVC )
   include ( ExternalProject )
   set( EXTERNAL_ROOT ${PROJECT_SOURCE_DIR}/external CACHE PATH "Location to clone third party dependencies to" )
   set( THIRD_PARTY_GIT_URL "https://github.com/mantidproject/thirdparty-msvc2015.git" )
-  set ( THIRD_PARTY_GIT_SHA1 0110e28aecbecc5602ede2031c492974fe568675 )
+  set ( THIRD_PARTY_GIT_SHA1 39a9535ce1320e49c6c34f9146e4cc140b31eca7 )
   set ( THIRD_PARTY_DIR ${EXTERNAL_ROOT}/src/ThirdParty )
   # Generates a script to do the clone/update in tmp
   set ( _project_name ThirdParty )
@@ -65,8 +65,14 @@ if( MSVC )
   unset ( _tmp_dir )
 
   # Print out where we are looking for 3rd party stuff
-  set ( PYTHON_MAJOR_VERSION 3 )
-  set ( PYTHON_MINOR_VERSION 8 )
+  option ( WITH_PYTHON3 "If true then build against Python 3.8" OFF )
+  if ( WITH_PYTHON3 )
+    set ( PYTHON_MAJOR_VERSION 3 )
+    set ( PYTHON_MINOR_VERSION 8 )
+  else()
+    set ( PYTHON_MAJOR_VERSION 2 )
+    set ( PYTHON_MINOR_VERSION 7 )
+  endif()
   set ( THIRD_PARTY_BIN "${THIRD_PARTY_DIR}/bin;${THIRD_PARTY_DIR}/lib/qt4/bin;${THIRD_PARTY_DIR}/lib/qt5/bin;${THIRD_PARTY_DIR}/lib/python${PYTHON_MAJOR_VERSION}.${PYTHON_MINOR_VERSION}" )
   message ( STATUS "Third party dependencies are in ${THIRD_PARTY_DIR}" )
   # Add to the path so that cmake can configure correctly without the user having to do it
diff --git a/buildconfig/CMake/WindowsNSIS.cmake b/buildconfig/CMake/WindowsNSIS.cmake
index 9e896bb0cb53039908415d44a62a1152cc3bdf0b..400a70737ad1a937bc1a5eb00157ef4071ec6a4f 100644
--- a/buildconfig/CMake/WindowsNSIS.cmake
+++ b/buildconfig/CMake/WindowsNSIS.cmake
@@ -60,11 +60,16 @@ mark_as_advanced(WINDOWS_DEPLOYMENT_TYPE)
 set ( BOOST_DIST_DLLS
     boost_date_time-mt.dll
     boost_filesystem-mt.dll
-    boost_python27-mt.dll
     boost_regex-mt.dll
     boost_serialization-mt.dll
     boost_system-mt.dll
 )
+if ( WITH_PYTHON3 )
+  list( APPEND BOOST_DIST_DLLS boost_python38-mt.dll )
+else ()
+  list( APPEND BOOST_DIST_DLLS boost_python27-mt.dll )
+endif ()
+
 set ( POCO_DIST_DLLS
     PocoCrypto64.dll
     PocoFoundation64.dll
diff --git a/scripts/Inelastic/QLdata_win64.cp38-win_amd64.pyd b/scripts/Inelastic/QLdata_win64.cp38-win_amd64.pyd
new file mode 100644
index 0000000000000000000000000000000000000000..68170025432c02fcf2e4375c7e8b808d121c18c0
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diff --git a/scripts/Inelastic/QLres_win64.cp38-win_amd64.pyd b/scripts/Inelastic/QLres_win64.cp38-win_amd64.pyd
new file mode 100644
index 0000000000000000000000000000000000000000..a05effad32b68e5f8337836553e1ff9aea0ad4c7
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diff --git a/scripts/Inelastic/QLse_win64.cp38-win_amd64.pyd b/scripts/Inelastic/QLse_win64.cp38-win_amd64.pyd
new file mode 100644
index 0000000000000000000000000000000000000000..f26afeee8cf8c299bfdf934b0bc2a3a597c56b55
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diff --git a/scripts/Inelastic/Quest_win64.cp38-win_amd64.pyd b/scripts/Inelastic/Quest_win64.cp38-win_amd64.pyd
new file mode 100644
index 0000000000000000000000000000000000000000..7c02c7a842f4911c3279a8e0dbb9c929e4071d92
Binary files /dev/null and b/scripts/Inelastic/Quest_win64.cp38-win_amd64.pyd differ
diff --git a/scripts/Inelastic/ResNorm_win64.cp38-win_amd64.pyd b/scripts/Inelastic/ResNorm_win64.cp38-win_amd64.pyd
new file mode 100644
index 0000000000000000000000000000000000000000..7daae32de8642e428ca5deecee245a8632d1e4b4
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diff --git a/scripts/Inelastic/cylabs_win64.cp38-win_amd64.pyd b/scripts/Inelastic/cylabs_win64.cp38-win_amd64.pyd
new file mode 100644
index 0000000000000000000000000000000000000000..49f51382e30f7c123199b4f0509278381c81834a
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diff --git a/scripts/Inelastic/muscat_win64.cp38-win_amd64.pyd b/scripts/Inelastic/muscat_win64.cp38-win_amd64.pyd
new file mode 100644
index 0000000000000000000000000000000000000000..7eeaf0122037daccf6b6212635df82bb91306d58
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