I'm lead to believe this dumping carried on for a lot longer, probably the 1970's.
A contact (ex V Force) told me of endless hours he spent on race tracks over the North Sea, dropping one at a time. The reason being that they were worried
that if one 'cooked off' sympathetic detonation would walk the big bangs up the stick to the carrier aircraft.
Fast forward 20+ years and I spent a fairly tense weekend in the company emergency control centre. A bottom survey had found a 1,000 lb bomb
very close to one of our major gas trunk lines. The Royal Navy came out, moved it away a mile or so and let it off. Quite and impressive bang. I always
wondered if this was a WW2 souvenir, or something more recent...….