A secret code hidden on the side of a Great Western Railway train remains unsolved despite a public appeal inspired by one of Britain's greatest codebreakers.

The railway operator launched a competition last week challenging members of the public to uncover a concealed message hidden within the livery of one of its Intercity Express Trains before the anniversary of Alan Turing's birthday on Tuesday, June 23.

The train, numbered 800008, was named after the pioneering mathematician and computer scientist in May 2022 and carries a special rainbow-themed design celebrating the LGBTQ+ community.

However, GWR has now revealed that a coded message incorporated into the train's artwork has remained undiscovered for the past four years.

The challenge has attracted plenty of interest from would-be codebreakers, with participants submitting a range of theories and possible solutions. While some eagle-eyed entrants have identified a tribute to Turing's school friend Christopher Morcom hidden within the design, the main message has yet to be deciphered.

In an effort to help crack the mystery, GWR has released a third clue.

It 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!"

The railway operator hopes the additional hint will inspire a final breakthrough before the competition closes on June 23.

A closer look at the hidden code embedded within the Alan Turing-themed Trainbow train, which has so far resisted attempts by the public to crack its secret message.
CYPHER: A closer look at the hidden code embedded within the Alan Turing-themed Trainbow train, which has so far resisted attempts by the public to crack its secret message. (GWR)

Dr David Kenyon, research historian at the Bletchley Park Trust, said the challenge was a fitting tribute to Turing's achievements.

He 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."

Dan Panes, GWR's head of external communications, said the response had shown just how much interest there remains in Turing's legacy.

He said: "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 solves the code before June 23 will be entered into a prize draw to win one of five limited-edition commemorative coins produced to mark the train's naming.

The competition has generated discussion across social media, with railway enthusiasts, puzzle fans and amateur historians all attempting to uncover the hidden message before the deadline passes.

Turing is best known for leading the team at Bletchley Park that broke the German Naval Enigma code during the Second World War, work widely credited with helping shorten the conflict and save countless lives.

His pioneering research laid the foundations for modern computing and artificial intelligence. He was posthumously pardoned in 2013 after being convicted under laws criminalising homosexuality, with subsequent legislation known as Turing's Law extending pardons to thousands of others convicted under similar historical offences.