Big Read: The plot to fool the Nazis involving a corpse, a submarine and tragedy in Scottish waters.

Patched up and ready to return to her role fighting Britain’s bloody war on and under the water, HMS Seraph silently rose from the depths to take on board an unusual and highly secretive, if not very talkative, passenger.

What ensued was a bizarre and audacious wartime plot intended to dupe Hitler’s forces, gain vital ground in Europe and which would ignite a mystery – the kind which could easily have fallen from the pages of a spy novel - which lingers to this day.

Indeed, so ludicrous and daring was the British plan to take a corpse, dress it to look like a naval officer and plant fake documents to trick the Nazis into thinking the Allies were invading Greece and not Sicily, that Operation Mincemeat would go down in military history and inspire a succession of books and movies.

The latest telling of the story, starring Colin Firth and Matthew Macfadyen as the two officers in charge of the plot, is now on in cinemas across the land; a reminder that sometimes truth can be stranger than fiction.

But as cinema goers absorb the latest telling of the outlandish story of how British intelligence officers dreamed up their incredible plan, certain burning questions remain...

Such as who, exactly, was the unfortunate corpse at the heart of their plan?

Is it possible that this silent character who went on to change the course of the war, may have been a tragic victim of one of the Clyde’s most mysterious incidents?

And, as an aside, what did this Second World War cunning plan have to do with James Bond?

In Ardrossan cemetery, the graves of Royal Navy sailors lie side by side, victims of an horrific explosion on board HMS Dasher on March 27, 1943.

Originally intended as an American merchant vessel, the ship had been commissioned into the Royal Navy the previous year and hastily refitted to become an aircraft carrier.

She was at anchor off Arran and Ardrossan full of fuel and armed to the teeth. There was no enemy fire and no record of German U-Boats or aircraft in the area when an almighty explosion ripped her apart.

Of the 528 crew on board, 379 perished. Today the remains of the carrier rests 140 metres below the surface of the Firth of Clyde, a designated official war grave.

Of the 68 bodies recovered, 24 men were later buried at Ardrossan Cemetery. But, to the distress of their grieving families who even today still demand answers from the Government, the whereabouts of the other 44 has remained shrouded in mystery ever since.

Indeed, such were the wartime sensitivities over the incident at the time, that despite the explosion being visible for miles around and having sent debris 60ft into the air, a complete blackout was imposed on reporting and discussing the incident.

It was as if this most awful of incidents had not happened at all.

At around the same time in London, military thoughts were focused on regaining Nazi controlled areas of Europe by launching an attack from its southern underbelly: through Sicily and onwards to Italy, or Greece and the Balkans.

Plans to confuse the Germans were put in place; fake military manoeuvres were conducted in Syria, and false communications about troop movements were issued from Cairo.

British intelligence officer RAF Flt Lieutenant Charles Cholmondeley had taken inspiration from an earlier document, the so-called Trout memo, which suggested various ingenious plots and deceptions – including one which suggested the use of a decoy corpse - to trick the enemy.

Although published in the name of Rear Admiral John Godfrey, the Director of Naval Intelligence, the vivid imagination behind the highly creative scenarios is believed to be the work of his personal assistant, Lt. Commander Ian Fleming, creator of the most famous spy of all, James Bond.

Working with peacetime lawyer Commander Ewen Montagu, Flt Lieutenant Cholmondeley hatched the ‘Trout memo’ inspired plan to deposit a corpse with fake identity and false letters in Huelva, Spain, where German agents were known to operate.

The body would be clothed and made to appear as if he had died in an air crash, with a name, Major Martin, and documents which seemed to enemy eyes to confirm Allied efforts were focused on invading either Greece or Sardinia.

The only issue was where to find a suitable body?

The story – later supported by a number of official documents - goes that an MI5 agent found a suitable corpse in the form of a vagrant, described by Montagu as “a bit of a ne'er-do-well… the only worthwhile thing that he ever did, he did after his death”.

He was said to have perished after eating rat poison, however, there were initial concerns that he was too under-nourished to pass off as an officer and fears any medical examination by the enemy would raise suspicions.

Nevertheless, the body – years later named as Welsh vagrant Glyndwr Michael – was said to have been transported hundreds of miles north by refrigerated van to the Holy Loch, to be loaded on to the waiting HMS Seraph.

Within days, the sub was in the waters off Spain and the body – which the unsuspecting crew had been told by commander Lt Norman Jewell, was a secret meteorological device - released to float towards Huelva.

It was discovered the same day, April 30, 1943.

The plan apparently worked. The fake major’s equally fake papers made their way to Hitler, who declared that Greece, Sardinia and Corsica be defended “at all costs”.

Nazi forces were quickly redeployed from Sicily, opening the door to the Allies’ invasion, Operation Husky, on July 9.

Questions, however, were swirling over the mysterious Major Martin.

Lt Jewell, the last man to see the body before it was released into the sea, later told the Navy News that he did not believe claims about the man’s identity.

One curious element was HMS Seraph’s location: originally in Blyth, Northumberland for her refit, instead of waiting for the refrigerated van from London, she had sailed north and on to the Holy Loch to collect her cargo.

Why would the sub journey further north when, with a decomposing corpse in the equation, time was clearly of the essence?

One theory is that the plan was rapidly switched: the Welsh vagrant was not ideal while the loss of HMS Dasher presented the plotters with a source – albeit incredibly tragic – of newly deceased men.

Could one of those unfortunate souls have become Major Martin?

Amateur historians John and Noreen Steele, authors of The Secrets of HMS Dasher, spent years trying to peel back the veil of secrecy surrounding the vessel’s loss and the whereabouts of so many of the explosion’s victims.

Their investigations led them to crew member John ‘Jack’ Melville. A bank official and amateur operatic singer who, at 37, had chosen to enlist out of a sense of duty. His physique and age made him a perfect fit for Major Martin.

Although his body had been pulled from the water, and his father and widow both asked to have his remains returned to Galashiels, authorities had insisted he be buried close the scene of the disaster.

Anxious not to appear difficult, the family reluctantly agreed.

Sixty years after the loss of HMS Dasher, John Melville’s daughter, Isobel Mackay, was told of the authors’ theory that her father was, in the name of the 1956 Ronal Neame film of the Operation Mincemeat episode, The Man Who Never Was.

She had grown up visiting what she believed was his grave in Ardrossan, later taking her sons to pay their respects. Instead, it now seemed more likely that he was the mysterious Major Martin and his body lay not in Ayrshire, but in Spain.

In 2004, during a memorial service on board the current HMS Dasher, Dennis Barnes, a spokesman for the British Forces in Cyprus, acknowledged the likely link: “This was undoubtedly the first tribute by the Royal Navy to John Melville, the man who never was,” he said.

Former Head of the Royal Navy, Admiral Lord West, is one of many who believes there remain unanswered questions surrounding HMS Dasher and its link with Operation Mincemeat.

“Use of a corpse taken from Scottish waters would explain Montagu’s otherwise almost inexplicable journey to Holy Loch to deliver the body of the tramp,” he wrote recently in the Daily Telegraph.

“The operation was sensitive but using the body of a dead Royal Naval sailor, without informing the family, raises it to another level.”

Meanwhile, for the remaining families of HMS Dasher’s lost victims, brought ashore but not given the honour of a burial, with no war graves and nowhere for grieving loved ones to visit, the campaign to uncover what happened, goes on.

For them, Operation Mincemeat and events of spring 1943 are far from mere movie entertainment.