Alan Turing: who was the English Mathematician and why is he the face of new Bank of England £50 note?
The World War Two Enigma codebreaker Alan Turing will feature on the new £50 banknote which will be released on June 23 - the computer pioneer’s birthday.
The design of the Bank of England’s new £50 note - which features Second World War Enigma codebreaker Alan Turing - has been revealed today
The polymer design, with advanced security features, will be issued for the first time on June 23, which would have been the computer pioneer’s birthday.
He joins a line up of other famous faces including the Sir Winston Churchill £5, the Jane Austen £10 and the JMW Turner £20.
The paper £50 notes can still be used and there will be a six month notice period before the old paper £50 is withdrawn.
But who was the codebreaker and why has he been chosen as the face of the new £50 note?
Who was Alan Turing?
Mr Turing played a pivotal role in breaking the Enigma code at Bletchley Park, which helped end the Second World War.
It has been said that this helped to shorten the length of the Second World War by at least two years - saving millions of lives.
Born on June 23 1912, Mr Turing studied mathematics at King's College, University of Cambridge and in 1936 his work On Computable Numbers was seen as giving birth to the idea of how computers could operate.
His "Turing test" also examined the behaviour necessary for a machine to be considered intelligent - the foundation for artificial intelligence.
But perhaps Mr Turing's best-known achievement was his role in cracking the Enigma code.
What special features does the bank note have?
The note, like the £20, incorporates two windows and a two-colour foil, making it very difficult to counterfeit.
There is also a hologram image which changes between the words fifty and pounds when tilting the note from side to side.
The new note, like the polymer £10 and £20, will contain a feature to help people who are visually impaired to identify the denomination.
The new £50 note will feature the signature of Sarah John, the Bank's chief cashier.
She said: "This new £50 note completes our set of polymer banknotes.
"These are much harder to counterfeit, and with its security features the new £50 is part of our most secure series of banknotes yet. These security features are common across all our banknotes, so if you can check one, you can check them all."
Why has the Bank of England chosen Alan Turing?
Bank governor Andrew Bailey said: "There's something of the character of a nation in its money, and we are right to consider and celebrate the people on our banknotes.
"So I'm delighted that our new £50 features one of Britain's most important scientists, Alan Turing.
"Turing is best known for his codebreaking work at Bletchley Park, which helped end the Second World War. However, in addition he was a leading mathematician, developmental biologist, and a pioneer in the field of computer science. He was also gay, and was treated appallingly as a result.
"By placing him on our new polymer £50 banknote, we are celebrating his achievements, and the values he symbolises."
What is the Turing Challenge?
The Bank of England has collaborated with GCHQ on the intelligence and cyber agency's "toughest puzzle ever" - based on the Turing £50 banknote design.
GCHQ's Turing Challenge, a set of 12 puzzles, has been put together by intelligence staff at GCHQ.