The mass escape of Allied airmen from a German prisoner of war camp remains one of history’s most famous jail-breaks. Stalag Luft III was designed to be escape-proof but PoWs, using impressive ingenuity to remain undetected, dug a tunnel, then crawled their way to safety 30ft below the oblivious guards.

It was an amazing master-stroke of courage and endurance nearly 80 years ago in March 1944. Unfortunately, the tunnel stopped far short of the protective cover of the surrounding forest.

Emerging one by one, the men had to make a dash for it. This foiled the original plan to free the full 200 men.

Even so, the Nazis discovered that 76 hardy prisoners had broken out of their supposed fortress.

Their heroic act was immortalised on screen two decades later in the 1963 film The Great Escape, starring Steve McQueen, Richard Attenborough and James Garner.

Yet, it was not unprecedented.

Prisoners throughout history, both men and women, driven by an obvious desire for freedom, have plotted to escape from their confinement.

Seven hundred years ago in 1323 there was another Great Escape, this one from the massive fortress of the Tower of London. The story of Roger Mortimer, Earl of March, is no different, in its way, from that of the famous Allied PoWs.

Mortimer was not the first prisoner to escape from one of the most fearsome jails in the land, nor was he the last.

Since it was built in the 11th century, there have been perhaps 40 successful breakouts from the Tower of London.

Two Jesuit prisoners used a rope stretching across the moat, in spite of their hands being crippled by torture. And one Jacobite gentleman was aided and abetted into cross-dressing as a female visitor to fool the guards.

But not all who risked the dangers lived to tell the tale. In 1244, a Welsh rebel fell to his death from the White Tower, as the central keep is known.

And in the 17th century, Colonel Thomas Blood broke into the Tower to steal the Crown Jewels, only to be captured before he could flee.

But Mortimer’s escape on August 1, 1323, was a conspicuous success – a dramatic tale of secret letters, drug use, rope ladders and not least the scaling of two supposedly impregnable outer Tower walls. So who was he and why had he been locked up in the Tower?

Mortimer was the owner of vast estates in the Welsh Marches and in Ireland. At the beginning of the reign of King Edward II, he had been a loyal subject. That was until the royal favourite, Hugh Despenser, backed by the King, laid claim to lands in the Welsh Marches.

This would be a threat to the Mortimer influence, so he joined a rebellion and raised his banners against the favourite and against the King. Edward II considered this to be treason so Mortimer was arrested and carted off to the Tower.

When news was brought to him that his life was in danger, Mortimer planned his escape. He had been writing letters, smuggled out of the Tower, to rouse another rebellion across England. Some were intercepted and delivered to the King.

There was no better way for Edward II to solve the problem than to have the letter-writing plotter killed – hanged, drawn and quartered – as a lesson to all other would-be traitors. Better Mortimer was dead than alive to plot. For Mortimer, better that he risk a spectacular escape. In effect, escape or die.

The event was cleverly planned for the night of the Feast of St Peter ad Vincula. St Peter was the patron saint of the church in the Tower, and every year a feast was held. So the Tower garrison would be celebrating with food and alcohol.

Unlike the brave escapees from Stalag Luft, Mortimer had the promise of help from friends and collaborators both inside and outside the Tower.

During the feast, guards, including the Constable of the Tower, all indulging liberally in wine and ale, were drugged and put to sleep by an accomplice. With the guards comatose, Mortimer was free to escape. But how did he break out? Surely the Tower was impregnable, from within and without?

In fact, the Tower was not always the formidable fortress it might seem today.

Some of the inner buildings had been allowed to fall into a dilapidated state, with rain even coming through the roof of the royal apartments. In particular, the kitchen roof was in disrepair, its timbers needing to be replaced and all re-tiled. Until that was done, there were significant holes.

This was the perfect route for Mortimer’s escape. He was able to break out through the crumbling walls of his cell, from where he could easily reach the kitchens.

There were still major difficulties to overcome, but Mortimer had been supplied with rope ladders. Climbing out through a hole onto the kitchen roof, he scaled the inner curtain wall of the Tower into Water Lane. From there, with considerable athleticism, he could climb the outer wall to drop down to the bank of the Thames.

The drugged wine and beer obviously worked well.

While the prisoners of 1944 had to cope with the shortfall of their tunnel, Mortimer’s escape went perfectly to plan. Once on the banks of the Thames, all had been meticulously organised to get him out of England. Friends were waiting with a boat to row him across to the opposite side.

At a nearby mill, horses were ready and he was helped on his way, south towards the coast, to Portchester from where he took the waiting ship to the Isle of Wight, and then on to refuge in France. On learning of the escape, the King ordered a hunt for his enemy throughout the entire country, but to no avail.

But was one of his collaborators Queen Isabella herself? Did she warn Mortimer of her husband’s plan to have him executed?

We know she spent time in the royal apartments in the Tower, and eventually became his lover during a trip to France.

And the result of his escape? Mortimer’s wife Joan – suspected of being capable of stirring up rebellion in her husband’s name –was placed under restraint in Skipton Castle, Yorkshire.

His children too were imprisoned, the girls sent with their mother or to convents, the boys locked up in Windsor Castle.

Meanwhile, in France, Mortimer became the focus of attention for all who opposed the land-grabbing favourite Hugh Despenser. Eventually, three years after his escape, he was able to raise sufficient money and troops to aid his return to England, intent on recovering all the lands and titles that had been stripped from him.

With him came Queen Isabella who had been living at the court of her father, the King of France. There is little doubt that by the time of their return, they were lovers.

And the rest is quite another story. The success of this escape from the Tower would result in the forced abdication of the King, the ruling power in England passing into the hands of Roger Mortimer and Queen Isabella.

On his return to England, Mortimer acknowledged the importance of the intervention of St Peter. God and his saints had quite definitely been on his side.

He ordered the building of a chapel to St Peter ad Vincula within his castle at Ludlow, to give thanks for his escape. Although ruined, the chapel still exists.

Unlike the prisoners of the 1944 Great Escape, Roger Mortimer has never appeared in film, nor are there any paintings of him. But the story of his thrilling escape lives on, 700 years before the men of Stalag Luft chanced their own. Mortimer’s escape from the Tower is one of the most dramatic parts of my new novel, A Court of Betrayal – the connecting link between his treachery and his seizing power as King in all but name.

For this, I am grateful to the chroniclers of the day who wrote just as well as the modern historians who find the Mortimer story of courage, treason, and betrayal a captivating subject.

If Mortimer had not escaped, he would have certainly died in the Tower, and his line would have faded into obscurity.

What an impact this would have had on our English history… since, through the carefully arranged marriages of the Mortimer children and their descendents, the future Yorkist Kings of England, Edward IV and Richard III, were descended directly from Roger and Joan.

*A Court of Betrayal by Anne O’Brien (Orion, £20) is out now.

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