The steel caisson (right), collapse which caused the disaster, and the tangle of broken shoring in the dry dock at Chatham after the submarine Talent had been swirled 1,000 feet across the Medway on to a mudbank. The submarine was swept from the dry dock after the caisson, which blocks entrance to the dock, had given way. To seal the dock, the caisson is filled with water. 16th December 1954.