Paper Money

Bank of England’s next £50 bank note to depict mathematician Alan Turing

The Bank of England will honor a mathematician on its next £50 bank note, expected to be issued in 2021. Alan Turing was one of the pioneers of computer science and was instrumental in developing code-breaking equipment during World War II.

Images courtesy of Bank of England.

Mathematician Alan Turing will be the subject of the Bank of England’s new £50 polymer note. Governor Mark Carney made the July 15 announcement at the Science and Industry Museum in Manchester, where he presented a concept of what the back of the note will look like when it enters circulation, expected at the end of 2021. The reigning monarch, currently Queen Elizabeth II, is always on the face of English paper money.

Turing was chosen after a public process that yielded a total of 227,299 nominations, covering 989 eligible characters in the field of science. The Banknote Character Advisory Committee reviewed them and sent 12 to Governor Carney to make the final decision. 

Turing, at 5 to 1 odds, was not the favorite of English bookmakers. One bookie, William Hill, had physicist Stephen Hawking as the favorite, at odds of 7:4, followed by chemist Dorothy Hodgkin at 4:1. Turing, microbiologist Alexander Fleming, and mathematician Ada Lovelace were next at 5:1 odds.

Carney remarked, “Alan Turing was an outstanding mathematician whose work has had an enormous impact on how we live today. As the father of computer science and artificial intelligence, as well as a war hero, Alan Turing’s contributions were far ranging and path breaking. Turing is a giant on whose shoulders so many now stand.” 

The concept £50 note will differ from the eventual end result in numerous respects, particularly regarding the many security elements, which will not be revealed until just before the final note is ready. Parts the bank revealed in its press release include:

A photo of Turing taken in 1951 by Elliott & Fry that is part of the Photographs Collection at the National Portrait Gallery. 

A table and mathematical formulas from Turing’s 1936 paper “On Computable Numbers, with an application to the Entscheidungsproblem.” This paper is usually described as being a foundation of computer science. It sought to establish whether there could be a conclusive method by which any theorem could be determined to be provable or not using a machine. It introduced the idea of a “Turing machine” as a thought experiment of how computers could operate. 

The Automatic Computing Engine Pilot Machine, the National Physical Laboratory’s trial model of Turing’s design. The ACE was one of the first electronic stored-program digital computers. 

Technical drawings for the British Bombe, the machine specified by Turing as one of the primary tools used to break Enigma-enciphered messages during the war. 

A quote Turing gave to The Times on June 11, 1949, “This is only a foretaste of what is to come, and only the shadow of what is going to be.” 

Turing’s signature from the visitor’s book at Bletchley Park in 1947, where he worked during World War II. 

Ticker tape depicting Alan Turing’s birth date (23 June 1912) in the binary code of zeroes and ones. The concept of a machine fed by binary tape was featured in Turing’s 1936 paper. 

Hero, then charged with a crime

A Bank of England statement provided a synopsis of Alan Turing’s life and its significance. He provided the theoretical underpinnings for the modern computer. He was best known for his work developing code-breaking machines at the legendary Bletchley Park code-breaking center during World War II. He played a crucial role in the development of early computers at the National Physical Laboratory and later at the University of Manchester. He set the foundations for work on artificial intelligence by considering the question of whether machines could think. 

Turing was homosexual in an era when homosexual acts were a criminal offense in the United Kingdom. In 1952, at the age of 39, he pleaded guilty to a charge of indecency regarding his relationship with a 19-year-old man. Upon conviction, he was given the option of either prison or probation subject to his undergoing chemical castration treatment. His housekeeper found him dead on June 8, 1954, with a partially-eaten apple next to his bed. The cause of death was listed as cyanide poisoning and an inquest later concluded it was suicide. 

In 2009, Prime Minister Gordon Brown made an official public apology on behalf of the British government for “the appalling way he was treated.” Queen Elizabeth II finally granted him a posthumous pardon in 2013.

His legacy, the bank states, “continues to have an impact on both science and society today.” 

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