Andymate.
I do recall this tragic accident. There were 3 fatalities - the Squadron Commander, who was on the rumble seat and doing a check ride on the pilot, one of the navigators who's seat fired, and one in the GCA caravan. The pilot was very badly injured but survived. The other navigator, when the remains of the aircraft came to rest, found himself still strapped in with nothing in front of him and, I think, suffered a broken ankle. Will PM you with a few more details if you wish.