Cracking German codes to unravel Nazi intelligence was one of the most important operations of the Second World War, a mission undertaken by thousands of Britain’s best minds.
But for Alan Turing, the most celebrated of the Enigma codebreakers, it appeared little more than a diversion from his true love – the pursuit of academic mathematics.
A notebook newly displayed at Bletchley Park in Buckinghamshire reveals Turing spent much of his spare time on his own work, unpicking and commentating on the language of mathematics itself.
The 39-page book, privately bought last year for one million dollars and on loan to Bletchley Park, is thought to have been written when Turing was using his genius to decipher German codes.
But in his down-time he wrote Notes On Notations, a commentary on methodologies of other leading 20th Century mathematicians.
His nephew, Sir Dermot Turing, said: “It’s quite clear that he saw the code-breaking activity as a sort of fun pursuit to be fitted in around the intervals of doing what he considered to be his real profession, which was academic mathematician.”
He added: “This notebook is one of the things that he put together roughly at the same time that he was working on the Enigma problem. It is all about challenges that he saw in the way that we write down mathematical formulas.
“He thought that some things were completely counter-intuitive, so he is writing a critique about the way mathematicians write down their ideas. It’s very different from the whole Enigma story that he was working on at the same time.”
The notebook, one of just a handful of Turing’s written manuscripts in existence, reveals his wry approach to the way formulae were written by his contemporaries.
He regarded some notation as “ugly” and “rather abortive”, dismissing another as “somewhat to be deplored”.
Sir Dermot said while the subject matter hindered deep psychological insight into Turing, the notebook revealed something of a sense of humour.
Turing left the notebook to close friend and student Robin Gandy, who wrote down his own dreams about Turing in a blank middle section.
Dr David Kenyon, research historian at Bletchley Park, said it was hard to overestimate the importance of Turing’s codebreaking techniques.
He said: “While codebreaking is absolutely vital for World War II and one of the most serious undertakings of the British government, Turing is thinking about something else a lot of the time.”