One of the biggest secrets of World War II was the Allied plan for the invasion of mainland Europe. Codenamed “Operation Overlord” and commanded by General Dwight D. Eisenhower, D-Day’s details were kept strictly on a need-to-know basis. For that reason, military leadership became quite alarmed when the most closely-guarded secrets started to show up in the crossword puzzles of a London newspaper.

Leonard Dawe was the creator of the crossword puzzles in question. He developed the puzzles for the Daily Telegraph from his study in his home. Writing crossword puzzles was more of a hobby than a calling. His day job was headmaster of Strand School, which had been evacuated to Effingham, Surrey. The school was situated next to a large camp of US and Canadian troops preparing for D-Day. This would give excellent access to anyone who had plans for espionage.

Dawe’s puzzles had already raised eyebrows among the powers that be. On August 18, 1942, the day before Operation Jubilee, an Allied attack on the port of Dieppe, France, the word “Dieppe” appeared as the answer to one of Dawe’s puzzle clues.

For this reason, military intelligence already had one eye on Dawe’s puzzles as the plans for the Normandy invasion neared finality. The concern intensified when the words “Gold,” “Juno,” and “Sword” all appeared in the months leading up to the planned invasion. These words were the codenames for the French beaches assigned to British and Canadian forces under the Overlord plan. British Secret Services started watching Dawe’s puzzles very carefully and grew increasingly concerned.

With D-Day scheduled for June 5, 1944 (it would be postponed until June 6 because of weather), Dawe’s puzzles increasingly seemed to suggest that someone had revealed some top secret information:

• May 2, 1944: ‘Utah’ (17 across, clued as “One of the U.S.”): code name for the D-Day beach assigned to the US 4th Infantry Division (Utah Beach).

• May 22, 1944: ‘Omaha’ (3 down, clued as “Red Indian on the Missouri”): code name for the D-Day beach to be taken by the US 1st Infantry Division (Omaha Beach).

• May 27, 1944: ‘Overlord’ (11 across, clued as “[common]… but some bigwig like this has stolen some of it at times.” — code name for the whole D-Day operation: Operation Overlord)

• May 30, 1944: ‘Mulberry’ (11 across, clued as “This bush is a centre of nursery revolutions.” —  Mulberry harbor)

• June 1, 1944: ‘Neptune’ (15 down, clued as “Britannia and he held to the same thing.” — codeword for the naval phase: Operation Neptune).

One of the crossword puzzles that contained clues related to the details of the D-Day invasion plans.

Thus convinced that Dawe had to be a spy, MI5 arrested him at the school. They also arrested his senior colleague crossword compiler, Melville Jones, at his home in Bury St Edmunds. After intensive investigation, MI5 reached its conclusion: it was all a big coincidence.

Investigators confirmed that Dawe’s practice in developing his crossword puzzles was to ask schoolboys to fill in his blank puzzles with words. Afterward, he would develop clues to fit the words the boys had provided. Investigators speculated that the boys may have overheard comments from soldiers on the nearby base, but never suspected that the words had anything to do with anything of a secret nature. Dawe later asked one of the boys, Ronald French, where he got the words he provided. French showed him a notebook that was filled with words he overheard from soldiers. Dawe ordered French to burn the notebook and made him swear on the Bible that he would not disclose any of the information he overheard from any of the soldiers. Dawe himself kept the details of the matter secret until 1958 when he was interviewed by the BBC.

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