HISTORIANS are appealing for the veteran codebreakers of Bletchley Park to volunteer for one last act of service for their country: cracking the D-Day carrier pigeon cipher that has stumped Britain's finest minds.

The coded message had been carefully filed in a small red capsule and attached to a carrier pigeon to be delivered 70 years ago.

But instead of arriving safely at its destination, the unfortunate bird got stuck in a chimney en-route and lost.

The message was found by homeowner David Martin, who ripped out a fireplace to find the skeleton while renovating his house in Bletchingley, Surrey.

Historians believe the bird was almost certainly dispatched from Nazi-occupied France on June 6, 1944, during the D-Day invasions.

The mysterious message, which was written in unfamiliar code, was passed to Government Communications Headquarter (GCHQ) in Cheltenham, Glos, in the hope a contemporary professional codebreaker could decipher the words.

Today, experts have admitted they have been unable to unravel the puzzle without knowing more about the cryptographic context in which it was sent.

They have now appealed to retired codebreakers who worked at GCHQ's predecessor, Bletchley Park, and others who may have worked in military signals, during the war to come forward to offer their expertise.

Those who are still alive are likely to be in their nineties but their memories may be sharp enough to recognise the type of code used, and explain how it could be deciphered.

Amongst their number is Baroness Trumpington, 90, a Conservative life peer who worked in Naval Intelligence at Bletchley Park.

A GCHQ historian, known only as Tony for security reasons, told BBC Radio 4's Today Programme it would be easier to identify the code if anyone could provide further information.

"We know in other contexts that there are still quite a lot of people alive who worked in communication centres during the war," he said.

"It would be very interesting if people did have any information if they could put it in the pot and we could see if we can get any further with it.

" He explained modern codebreakers had so far been stumped by the secret message, with no clues as to who sent it or who was intended to receive it.

He added: "The sort of codes that were constructed to be used during operations were designed only to be read by the senders and the recipients.

Unless you get rather more idea than we have about who actually sent the message and who it was sent to we are not going to be able to find out what the underlying code was.

" The message in full reads:

AOAKN HVPKD FNFJW YIDDC

RQXSR DJHFP GOVFN MIAPX

PABUZ WYYNP CMPNW HJRZH

NLXKG MEMKK ONOIB AKEEQ

WAOTA RBQRH DJOFM TPZEH

LKXGH RGGHT JRZCQ FNKTQ

KLDTS FQIRW AOAKN 27 1525/6

It is believed to have been dispatched by British forces during the D-Day invasion to relay secret messages back across the Channel, after a radio blackout left them reliant on homing pigeons.

The Royal Pigeon Racing Association believe the bird probably either got lost, disorientated in bad weather, or was simply exhausted after its trip across the Channel.

Due to Winston Churchill's radio blackout, homing pigeons were taken on the D-Day invasion and released by Allied Forces to inform military Generals back on English soil how the operation was going.

Speaking earlier this month, Mr Martin said: "It's a real mystery and I cannot wait for the secret message to be decoded. It really is unbelieveable."

It is thought that the bird was destined for the top secret Bletchley Park, which was just 80 miles from Mr Martin's home.

The message was sent to XO2 at 16:45.

The destination X02 was believed to be Bomber Command, while the sender's signature at the bottom of the message read Serjeant W Stot.

Experts said the spelling of Serjeant was significant, because the RAF used J, while the Army used G.

Pigeon enthusiasts - commonly known as "fanciers" - have called for Mr Martin's mysterious military bird to be posthumously decorated with the Dickin Medal; the highest possible decoration for valour given to animals.

The dead pigeon was likely to be a member of the secret wing of the National Pigeon Service - which had a squadron of 250,000 birds during the Second World War.

They can reach speeds of 80mph, cover distances of more than 1,000 miles and are thought to use the Earth's magnetic fields to navigate.

The Telegraph