Classified records turn up in the strangest places.

Some forty tears ago, a Canadian submarine skipper died and left his professional papers to the Public Archives (as it then was). The collection was packed up at the old salt’s house in Esquimalt, trucked to Ottawa, and in due course accessioned. It came to me, then a student on a four-month stage, to be “arranged”, as they say in the racket.

Three cubic-foot storage boxes and two weeks into the project, I found a four-inch file box tightly packed with Secret and Top Secret documents about nuclear warheads for torpedoes and performance studies of the then brand-new Oberon class of diesel-electric boats.

After his command tour, the skipper was posted to the Operations branch at Naval Headquarters. It was deep in the Cold War and a time of frantic security theatre, but he nevertheless took work home — and forgot some of his reference materials.

The world continued to revolve on its axis.