Missing Crew Negative Photos

My Uncle Herbert Delacour was an Australian Pilot Officer with the RAF 514 Bomber Command Squadron at Waterbeach UK. His plane was shot down after ccompleting their last mission and sadly was killed. There were 3 surviving crew members and there were negative photos kept in the locked of one of these men. But when his belongings were returned to his parents the negatives were not to be found.
I know this is a very slim chance but is there an area within the RAF or Defence department that I can direct my enquiry to in a hope to retrieve these photos?

Cheers
Dellie