A submarine story about collecting enemy weapons

What was the story about mysterious German or Italian weapons arriving at a British base?

The remembered episode concerns sailors collecting equipment crates from a coastal station for their submarine, without an official document confirming it.

British special operations needed enemy weapons, and captured stocks supplied some of that equipment. Asked about mysterious crates reaching a British base, Alex recalls a submarine-service account in someone's personal notes. In that story, sailors went ashore to a coastal station, collected crates from a wagon, and brought the equipment back aboard their submarine. He has never found an official document confirming the episode, so the story remains anecdotal.