There was an electrical circuit in the Gnat whose purpose was to limit maximum aileron angle at high speed. The circuit was fused by (I think) 'Fuse 13'. A member of the Red Arrows realised that if the fuse was removed, full aileron and an exceptionally high 'twinkle' roll rate would be achievable. They tried it - it did indeed work...
However, 'the girls' (i.e. A squared E squared) were concerned about both inertial coupling and fin stress resulting from such violent rolls; their counsel prevailed and orders were issued that the Reds' fuses were to be re-fitted. But no-one had said that the fuses had to be replaced 'serviceable'.....
Sadly, a Gnat did lose its fin at low level after a twinkle roll and the crew were killed. The fuses were all replaced with serviceable ones.