XP831 Ist Hawker P1127 Prototype now hanging from ceiling of the South Kensington Science Museum. The 6th and final P1127 was the standard of the Kestrel. There was no prototype Harrier, XV276 being the first of six development P1127(RAF) aircraft subsequently named Harrier
44 years later this is the latest great great grandson of XP831.
The Harrier GR9 has a mere 3000 lbs thrust more than the GR7 in ISA+35 (yes that is correct 50 deg C).