I'm not sure if anyone else has seen it however there is another video somewhere which shows the footage from a few seconds earlier, I'll see if I can find it.
Edit, see here.
http://www.telegraph.co.uk/news/avia...s-CarFest.html
Hard to see what's going on due to the quality but it looks like it starts with the aircraft performing an aileron roll which looks normal, it then rolls to the left but overbanks quite significantly, looked like about 120-130 degs which is then corrected back to 90 degs but is pulling by this point, its from here the other footage starts and you know the rest. In the slow motion however in the latter stages it looks like he very briefly starts to roll to the right immediately before the rapid roll to the left.
Never flown the Gnat however is there a failure more which leaves the controls still boosted but lacking artificial feel?
Regards
UA