This was a hideous accident and certainly not one to be flippant about.
I was onboard at the time and the accident shook us all, especially as the observer was a splendid character, well-liked by all.
The aircraft had a problem that developed to the extent that the crew had to leave it. The Vixen seat / hatch combination had given problems before, and this time it resulted in the observer being stuck half-in / half-out of the aircraft as he struggled to manually bale out. Unfortunately, he did not make it, and his pilot left it incredibly late to eject, though he, fortunately, survived.
I have left out further details, including the names of the crew out of respect for the observer.
GW