The Bank of England revealed the note’s design featuring the scientist and mathematician, as GCHQ officials unveiled the new treasure hunt involving 12 puzzles which they say “might even have left him scratching his head”.

Experts have said it will take even the most experienced puzzlers at least 7 hours.

For all the clues if you fancy giving it a go, visit the GCHQ website HERE, or scroll to the bottom of this page.

Alan Turing is perhaps best known for his code breaking work during the Second World War. In recognition of this, the Bank of England has collaborated with GCHQ on the intelligence and cyber agency’s toughest puzzle ever.

Alan Turing is perhaps best known for his code breaking work during the Second World War. In recognition of this, the Bank of England has collaborated with GCHQ on the intelligence and cyber agency’s toughest puzzle ever.

The note will go into circulation for the first time on 23 June 2021, which coincides with Mr Turing’s 99th birthday.

Mr Turing was a pioneer of modern computing and hugely instrumental in breaking the German Naval Enigma cipher in 1942, at Bletchley Park – GCHQ’s wartime home.

But despite all he did for the war effort and the countless lives he would have saved by his genius, he was persecuted by the Government in the years after the war because he was gay.

In January 1952, Mr Turing was prosecuted for “indecency” over his relationship with another man in Manchester, and was given a choice between imprisonment and probation on condition of undergoing hormone treatment.

Sarah John, Chief Cashier at the Bank of England, holding the new £50 note featuring scientist Alan Turing

Sarah John, Chief Cashier at the Bank of England, holding the new £50 note featuring scientist Alan Turing. Picture: PA

In 1954, Mr Turing took his own life.

Director of the cyber and intelligence agency Jeremy Fleming described him becoming the first gay man to appear on a banknote as confirming his status as “one of the most iconic LGBT+ figures in the world”.

Mr Fleming said: “Alan Turing’s appearance on the £50 note is a landmark moment in our history.

“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.

“Turing was embraced for his brilliance and persecuted for being gay.

“His legacy is a reminder of the value of embracing all aspects of diversity, but also the work we still need to do to become truly inclusive.”

The puzzles are based on the unique design elements of the new banknote, such as the technical drawings for the British Bombe, the machine designed by Mr Turing to break Enigma-enciphered messages.

GCHQ officials said the full challenge could take an experienced puzzler seven hours to complete.

Colin, a GCHQ analyst and its chief puzzler, said: “Alan Turing has inspired many recruits over the years to join GCHQ, eager to use their own problem-solving skills to help to keep the country safe.

“So it seemed only fitting to gather a mix of minds from across our missions to devise a seriously tough puzzle to honour his commemoration on the new £50 note.

“It might even have left him scratching his head – although we very much doubt it.”

Mr Turing joined the Government Code & Cypher School – GCHQ’s wartime name – in 1938 to help with the code-breaking effort during the Second World War, working alongside Gordon Welchman.

In January 1940, Mr Turing had a meeting in Paris with Polish counterparts, who gave him the insights he needed to design the Bombe.

The combination of the Bombe and the brilliant minds and perseverance of those working at Bletchley Park led to the breaking of Enigma.