The UK's new £50 note has started to enter into circulation from today, featuring the image of mathematician Alan Turing.
The Bank of England says the design is "a recognition of his contributions to our society, and a celebration of his remarkable life."
Turing is often considered to be the father of computer science, having played a pivotal role in the Second World War to break the Germans' Enigma code.
He is also the first LGBT person to feature on a UK banknote.
Government Communications Headquarters (GCHQ), the British intelligence organisation Turing worked for, has marked the release of the note by installing a giant rainbow-inspired artwork at its base in Benhall, Gloucestershire, and the Bank of England is flying the Progress Pride flag on its building on Threadneedle Street in London.
The new polymer note will become available in bank branches and at ATMs in the coming days and weeks.
The remarkable life of Alan Turing
Born on 23 June 1912, Turing went on to study mathematics at King's College, University of Cambridge, gaining a first-class honours degree in 1934. A year later he was elected a Fellow of the College.
His 1937 paper, On Computable Numbers, is often credited with having given birth to the idea of how computers could operate.
While working at Bletchley Park in Buckinghamshire during the Second World War, Turing and his team designed a deciphering machine, the Bombe, that was pivotal to the decoding of the Enigma machine.
His invention, which enabled the British security services to read the Germans' secret messages, is said to have helped to shorten the war by at least two years – saving millions of lives.
The breaking of Enigma was later turned into a 2014 film, The Imitation Game, starring Benedict Cumberbatch as Turing.
Turing's legacy also includes setting the foundation for artificial intelligence, with his 'Turing Test' examining the behaviour necessary for a machine to be considered intelligent.
The wartime hero's later life was overshadowed by a conviction for homosexual activity, which was later considered unjust and discriminatory.
Turing was convicted of "gross indecency" for his relationship with a man, which led to the removal of his security clearance and meant he was no longer able to work for GCHQ.
He was chemically castrated following his conviction in 1952 and died in 1954 at the age of 41.
He was later given a posthumous royal pardon.
"Turing was and remains a beacon of hope for all who dare to live and think differently"
Turing now joins Sir Winston Churchill, Jane Austen and JMW Turner in an illustrious group whose lives and contributions to history are honoured on the UK's next generation of polymer banknotes.
Speaking at Bletchley Park, Bank of England governor Andrew Bailey said: "Our banknotes celebrate some of our country's most important historical figures.
"That's why I am delighted that Alan Turing features on the new polymer £50 note.
"Having undertaken remarkable codebreaking work here at Bletchley Park during the Second World War, he went on to pioneer work on early computers, as well as making some groundbreaking discoveries in the field of developmental biology.
"He was also gay and was treated appallingly as a result. Placing him on this new banknote is a recognition of his contributions to our society, and a celebration of his remarkable life."
The Bank of England Museum has also launched an online exhibition to coincide with the Turing £50 banknote entering circulation.
GCHQ director Sir Jeremy Fleming said: "Alan Turing was a genius who helped to shorten the war and influence the technology that still shapes our lives today.
"He was embraced for his brilliance but persecuted for being gay.
"Turing's legacy reminds us every day that diversity is essential and inclusion is mission critical to our organisation.
"Turing was and remains a beacon of hope for all who dare to live and think differently."
