Here are a couple of links to the RAF Fauld bomb dump explosion of 1944.
Wikipedia Link to Fauld Explosion
Tutbury History Site
Contemporary Aerial View of Fauld Crater
The moral of the story being don't tinker with bombs using incorrect tools. I'm guessing that much of the ordnance stored here wasn't fused, yet it still exploded after the incident with the initial fused bomb. Could this occur with the ordnance on the Sheerness Liberty Ship? An initial explosion (by whatever means - chemical degradation, lightning strike, diving activity etc) triggering the rest of the cargo.
JMB