OK, I cant for the life of me remember where I read/heard about spitfires going supersonic during dog fight.
I wonder if I was "got" by some sensationalised documentary perhaps?
Aaanyway, done a quick google search and the closest I can find to anything like that is a post from someone on another forum (on the same subject) explaining that although the aircraft would not actually be exceeding mach 1, his instruments may say that he is, inaccuracies and what-not. This would lead to pilots genuinly believing they had broken the sound barrier.
Sorry for being naive, I shall be sure to check for substance behind these random "facts" that I seem to memorise, before posting next time
JB