Simon Callow's Codebreaker Surprise

Thespian’s university tutor was influential Codebreaker, John Herivel.

The distinguished actor, Simon Callow, has told the Bletchley Park Trust about the surprising secret held by his university tutor.

Simon was asked by BBC Daily Politics to make an authored film about Russia’s anti-gay laws, highlighting the story of Alan Turing.

While filming at Bletchley Park, Simon spoke to the Bletchley Park Podcast. He went to Queens University in Belfast in 1968 and his tutor was none other than World War Two Codebreaker, John Herivel. In February 1940 he devised the Herivel Tip, which relied on understanding human nature. He imagined a German Enigma operator waking at midnight to set the new key of the day. He worked out that the rotor settings would only be varied by a few letters, if at all, rather than entirely randomly, as per the instructions. His realisation was a key breakthrough.

Simon only discovered John Herivel’s fascinating history after he died, when he read his book. He says “I was absolutely astonished. He was a wonderful teacher, in the old fashioned way. During his tutorials he used to make tea and toast crumpets by the fire. (He was) a very profound thinker but very unexpected in his approaches but there was no sense that he had done anything extraordinary with his life. That was his generation; they didn’t kiss and tell.”

John Herivel was a Cambridge mathematician recruited to Bletchley Park by Gordon Welchman. He later became a fellow of All Souls in Oxford and died in 2011 aged 92.