In late 1941, a mysterious Mr Gavin wrote to the Daily Telegraph offering £100 to be donated to charity if anyone could solve this crossword in less than 12 minutes. The competition was to be held at the Telegraph’s office in Fleet Street, London.

A few weeks later those who managed it received letters asking them to report to Military Intelligence (that well-known oxymoron), which then sent them on to Bletchley Park.

This recruitment method would never get past HR nowadays. But then, there was a war on.

(As you can see, someone in our house has been having a go at it!)

It’s different from the cryptic puzzles one finds nowadays in the posher newspapers — it’s a mixture of cryptic and quick clues.