Red Arrows....John Haddock
The "illegal modification" to the controls just meant that the Red Arrows Gnats (as opposed to the ones at 4FTS Valley), had the aileron limit stops taken out. With the stops in the roll rate was about 250deg per sec; with them out it was about 400. A pretty snappy roll rate. Of course, you could enhance the roll rate of the 4FTS Gnats by using a bit of rudder with aileron, but - sensibly - this was strongly advised against in the aircrew manual because of the risk of roll divergence.
This was demonstrated graphically when a 4FTS Gnat instructor spread himself and his aircraft all over Gaydon airfield after initiating a "twinkle" roll with added rudder at high speed. The aircraft diverged, went flat plate and disintegrated.
Ex MM