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It’s been hidden on the side of a train for the past four years, so no wonder a secret code paying tribute to World War Two codebreaker Alan Turing has proved a tough nut to crack.

Great Western Railway last week launched a competition for would-be codebreakers to try to uncover the message before the anniversary of Turing’s birthday on 23 June.

The train operator named its popular ‘Trainbow’ Intercity Express Train after the pioneering computer scientist back in May 2022.

After revealing there was a secret message hidden within the livery on IET^▸ (Intercity Express Train - replacement for HSTs (manufactured by Hitachi in Kobe, Japan)) 800008, plenty of people have come forward with guesses and theories – but still the code is unbroken.

Some eagled-eyed participants have found the tribute to Turing’s school friend – ‘For his love of Christopher’ – but the main message is still to be cracked.

Now GWR^▸ (Great Western Railway) is providing a further helping hand by revealing a third clue, which confirms the correct sequence of letters used in the hidden message.

The latest clue reads: “Remember the second clue (the palindrome 800008) and if you think there are too many ‘Z’s, make some SPACE – it may make things clearer!”

Bletchley Park Trust Research Historian, Dr David Kenyon, said: “It’s fitting that Alan Turing has been honoured in a way that reflects his extraordinary codebreaking skills and sheer determination. He and his colleagues at Bletchley Park faced problems that seemed genuinely unsolvable. Turing never shied away from a seemingly impossible problem and neither it seems is the public.”

GWR Head of External Communications, Dan Panes, added: “We knew we were setting people a proper challenge when we revealed there was a hidden message on the train. We’ve had lots of guesses and some very clever ideas, but so far nobody has cracked it.

“With Alan Turing’s birthday looming ever closer, we thought it was time to offer an extra clue to see if that helps someone finally unlock the mystery.”

Anyone who works out the message before 23 June will be entered into a prize draw to win one of five limited-edition commemorative coins produced to mark the train’s naming.

Best known for his work at Bletchley Park during the Second World War, Turing led the team responsible for breaking the German Naval Enigma code, intelligence work that proved crucial to the Allied war effort.

His groundbreaking contributions to mathematics and computer science laid the foundations for modern computing and artificial intelligence.

Turing is also remembered as an important figure in the history of LGBTQ+ rights. Convicted under laws that criminalised homosexuality, he was subjected to chemical castration and died in 1954 aged 41.

Following a public campaign, he received a posthumous Royal pardon in 2013. The subsequent ‘Turing’s Law’ legislation led to pardons for thousands of other men convicted under historical laws that criminalised same-sex relationships.

The train was named by members of Turing’s family at London Paddington, where GWR also unveiled its ‘Trainbow’ livery celebrating the LGBTQ+ community.

First introduced in 2018, the rainbow-themed design continues to appear at Pride events across the network and reflects GWR’s support for LGBTQ+ colleagues, customers and communities.

Image credit: GWR