Gentlemen,thank you for all the information. I will now wrap up this thread. On the night of the 2nd March 1945 (yes 1945 not 1944) two Lancasters,carrying out a fighter affiliation exercise, collided over Ruskington Fen Farm, Lincolnshire. Sadly there were no survivors. The aircraft involved were: ME 473 belonging to 207 Sqn from RAF Spilsby and ND 572 belonging to 57 Sqn from RAF East Kirby. This was the crash witnessed by my old friend.
The 207 Sqn aircraft was a nearly new Mk 111 which I am told had 0.50cal guns fitted to the rear turret. In 1995 the site was excavated and some human remains were recovered. This discovery allowed the positive identification of some unidentified remains that were recovered during the post crash clear up of the site in 1945.