I don't know if it was a Martin-Baker ejection seat, but this pilot's account of surviving an ejection from 78,000 ft at Mach 3.18 (3926,664 km/h!) in a SR-71 Blackbird is pretty wild.
http://www.chuckyeager.org/news/sr-71-disintegrated-pilot-fr...
http://www.chuckyeager.org/news/sr-71-disintegrated-pilot-fr...
Minor nit pick, the pilot did not in fact eject. He was literally thrown out of the disintegrating aircraft, ripping his shoulder and waist harnesses in the process. Insane stuff, especially that he survived.
Were his knees bent the wrong way?
As an aside, the website (ejectionseat.com) is a trip itself.
Sad part of the story is that the other pilot of the original Blackbird incident didn't survive. The surviving pilot saw his companion's parachute and was thus (thinking that he survived) motivated to fight for his own life.