I can remember sitting in a very bad tempered 3 way meeting between HSA, Rolls Royce and MoD back in the 1970s or 80s. The issue was a Phantom pherry, if I remember rightly from Cyprus. Somewhere en route one of the Phantoms had an engine problem, either low oil pressure or vibration and the pilot throttled the engine back to idle. The pilot decided to continue the ferry but could not maintain station with the tanker with one engine at idle and one at Mil power. He therefore flew for around 2 hours with the good engine in reheat before landing safely back in the UK. The limitation in the books was that no more than 12 minutes in any hour could be spend at Mil power or above. Rolls Royce argued that this meant the limit had been grossly exceeded but the rest of us believed that provided the average over the life of the engine did not exceed 12 minutes in any hour it was OK. The argument raged for hours and I dont think it was ever resolved, but I dont think any harm came to the engine either. Whether the pilot got severely reprimanded as Rolls Royce requested seems unlikely.