Watch Graham Stothard's video report on Alan Turing becoming the face of the 50
The Bank of England has revealed the design for the new £50 note, featuring Bletchley Park codebreaker Alan Turing.
The note will enter circulation on June 23, which would have been the Cambridge mathematician's birthday.
Turing played a key role in helping to crack Nazi ciphers using the Enigma machine at Bletchley, now in Milton Keynes, during the Second World War.
His work is credited with shortening the length of the war, saving many lives in the process.
He will also become the first gay man to appear on a banknote.
"Alan Turing's appearance on the £50 note is a landmark moment in our history," GCHQ director Jeremy Fleming said.
"Not only is it a celebration of his scientific genius, which helped to shorten the war and influence the technology we still use today, it also confirms his status as one of the most iconic LGBT+ figures in the world."
GCHQ has created its toughest ever puzzle in honour of Alan Turing, with puzzlers warned it will take seven hours to complete.
The challenge appears on a new £50 note revealed by the Bank of England, featuring the scientist and mathematician who pioneered modern computing.
But for those who haven't yet got hold of one yet, GCHQ has put the puzzle online too.
The note will feature a quote from Turing that he gave in an interview with the Times in the 1940s, in which he said: "This is only a foretaste of what is to come, and only the shadow of what is going to be".
The new polymer note will also contain advanced security features.