IT'S been called the greatest episode of military espionage since the Trojan Horse and now the incredibly story of the Allied effort to dupe the Germans about the 1943 invasion of Sicily is being turned into a film.

Starring Colin Firth, and based on historian Ben MacIntyre's book, Operation Mincemeat: The True Spy Story That Changed the Course of World War II, the film follows two Allied intelligence officers who come up with a disinformation strategy involving the dead body of a homeless Welsh man, a fictitious army officer and a suitcase full of fake documents.

What's even more extraordinary is that the ruse worked, German reinforcements were shifted to Greece and Sardinia, and thousands of soldiers' lives were save. And unbelievably, the market town of Mold, in Flintshire, played its part in what came to be known as Operation Mincemeat.

Early in 1943 the Allies were anxious to build on their stunning military successes against Nazi Germany in North Africa.

The Anglo-American high command decided their next target should be Sicily from where they could leapfrog to the toe of Italy, fighting their way northwards into the heart of Hitler's Fortress Europe.

But the Allied leaders also knew invading Sicily presented a huge challenge and could easily end in a massive bloodbath if the German and Italian defenders knew the island was the target.

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The signing in book from The Black Lion Hotel, in Mold showing the entry for J.W.Martin bottom right.

British intelligence officers were therefore given the task of coming up with a plan to persuade the Axis powers that Greece - and not Sicily - was the invasion target.

If the enemy could be persuaded to fall for this ruse, they would then send reinforcements to the wrong place and the invaders of Sicily would face a much easier time.

A small team of British spies, based in Whitehall, had to create a deception that could potentially save the lives of thousands of Allied troops.

At its head was peacetime barrister and Royal Navy Commander Ewen Montagu and his deputy, Charles Cholmondeley, a highly intelligent yet eccentric RAF officer. Their idea was brilliantly simple, yet fiendishly difficult to make work.

They would dump a dead body on the coast of Spain, which would apparently be that of a British officer.

He would have been acting as a courier for the Allies when the plane in which he was travelling crash-landed into the sea.

The body would carry a sheaf of fake confidential letters between top Allied officers which made reference to an invasion of Greece by British and American forces.

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Black Lion, Mold

Spain was chosen as the place to have the body found as, although officially neutral, many of the rulers of the Fascist-controlled country were in fact highly sympathetic to the Nazis.

The part of the Spanish coast - at Huelva - was also known to be a hotbed of German spies who, it was hoped, would make sure the documents found their way into the hands of their masters.

The book describes how the elaborate deception plan - known by the codename Operation Mincemeat - came together after winning the approval of Winston Churchill.

A suitable body, that of a homeless man in his late 30s, was found by the team with the unofficial help of a coroner in London.

Glyndwr Michael had been born into a poor family in Aberbargoed in South Wales and wandered into a hopeless existence. He eventually drifted to London and died - either by suicide or by accident - by taking rat poison.

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Operation Mincemeat by Ben MacIntyre 

Montagu and Cholmondeley then spent weeks preparing his body for its service to the war effort. They came up with a name - Major William Martin - and around it wove an elaborate but completely fictional life history.

One important aspect of this was Major Martin's 'family', which would include his father, John G. Martin. To make the discovery of the body as authentic as possible, Major Martin would not only be carrying the top secret correspondence between the British generals but also personal letters, including one from his father. It would be penned just a few days before his son's death and refer to routine family matters.

It would also have to be sent from a hotel rather than a fictitious home address which Germans agents in Britain might be able to check as being the residence of a J.G.Martin.

The place chosen was the Black Lion on Mold's High Street, Mold. Built in the 18th century, the inn once stood in the heart of the market town and during its heyday had accommodation comprising 19 beds for the weary travellers and refreshments for about 100 people. Later the hotel was closed and became a Woolworths store. A reminder of the hotel's former existence can be seen in the pillars still standing outside.

Dated April 13, 1943, Montagu and Cholmondeley's letter began: "My Dear William, I cannot say that this hotel is as comfortable as I remember to have been in pre-war days..."

It went on to outline how Mr Martin intended to meet his son in London about a week later, when he hoped the two men could discuss complaints from the bank about the way the major was handling his personal finances. It ended: "Your affectionate Father."

A few months later, Major Martin's body was cast adrift from a submarine and was found by fisherman Jose Antonio Rey Maria.

As predicted, the Mold letter and other documents were soon passed to the Nazis, who dutifully arranged for massive reinforcements to be sent to Greece.

The invasion of Sicily went ahead with limited loss of life and achieved all its objectives, meaning Operation Mincemeat had been a dazzling triumph.

The official history of the Second World War later described it as "perhaps the most successful deception of the entire war".

However, in the postscript of MacIntyre's book, he describes how at one stage the men who put together the ruse must have had doubts about the Black Lion part of the plan.

They realised that if German agents were to check out the contents of the letter, they might send someone to Mold. A look at the hotel register for the time Mr Martin was supposed to have stayed there would reveal this completely fictitious character had never signed in.

To ensure this would not happen - and put the whole operation at risk - the author speculates one of the team must have travelled from London to North Wales to cover their tracks.

He believes this was the case because, soon after his book was published, he was shown a copy of the register by the un-named person who now has it in their possession. And there on the appropriate page is the signature of a J.G.Martin.

"But closer examination revealed something very odd," writes MacIntyre. "The name and signature of J.G.Martin did not appear in the correct date sequence, but was added in the space at the bottom of the page. It was clearly an afterthought, written in sometime afterwards. To even the most casual investigator this would have set off loud alarm bells: so far from covering up the mistake, Cholmondeley had compounded it, by drawing attention to the fact that there was something distinctly out of the ordinary about John Martin and his sojourn at the Black Lion."

In the end, it did not matter. There is no evidence that the Germans ever carried out any checking of the Bill Martin backstory. Had they attempted to do so, this would almost certainly have been picked up by British intelligence, since the entire German espionage system in the UK was effectively controlled by MI5.

"Still, it is sobering thought, that if a single German agent had travelled to Mold and examined the register of the Black Lion, he would surely have spotted the obvious addition of 'J.G.Martin', recognised there was something fishy going on, and warned the Germans before the invasion of Sicily," adds MacIntyre. "The island might then have been reinforced, and countless lives might have been lost with incalculable consequences. That single register entry could have changed the course of the Second World War."