A Flt Cdr of mine many, many years ago had spent his formative years on the Lightning at Leconfield and told the following story:-
When the U2s first came into the country, they claimed they flew so high nothing could get them---a challenge that had to be accepted. Initially they were coming in highish and were not happy to see the Lightnings sail past nor to be shown the the B-Scope film of the Mx shot. The U2s went higher and higher until eventually, my man claimed he went past the target, above 70,000 ft, supersonic, stalled and with a double fame out---just hope he had the pressure jerkin and helmet on!