Daily Telegraph crossword
On 17 August 1942, the clue "French port" appeared in the Daily Telegraph crossword (compiled by Leonard Dawe), followed by the solution "Dieppe" the next day; on 19 August, the raid on Dieppe took place. The War Office suspected that the crossword had been used to pass intelligence to the enemy and called upon Lord Tweedsmuir, then a senior intelligence officer attached to the Canadian Army, to investigate the crossword. Tweedsmuir, the son of John Buchan the author, later commented:
"We noticed that the crossword contained the word "Dieppe", and there was an immediate and exhaustive inquiry which also involved MI5. But in the end it was concluded that it was just a remarkable coincidence—a complete fluke".
A similar crossword coincidence occurred in May 1944, prior to D-Day. Multiple terms associated with Operation Overlord (including the word "Overlord" itself) appeared in the Daily Telegraph crossword (also written by Dawe), and after another investigation by MI5 this turned out to be a remarkable coincidence as well