"Tom" was discovered by the German guards and "Dick" was abandoned when a swathe of sheltering forest beyond the wire was cut down.

"Harry" became the most famed of all escape tunnels built during World War II.

On the night of March 25, 1944, 76 POWs slithered through it and struck out for freedom.

All but three were recaptured, but so audacious was the break-out that Hollywood turned it into a hugely popular film: The Great Escape.

The late American tough-guy actor Steve McQueen was the star.

He played the fellow who levied the boards from prisoners' beds to shore up the tunnel.

Truth is, no American took part in the great escape.

It was a young Australian air ace, John Williams, who persuaded his fellow POWs to sacrifice the thousands of wooden boards that were supposed to support their mattresses – the Germans later discovered 4000 boards had gone missing underground, plus 90 bunk beds and 62 tables.

Williams, who had built his own wooden surfboards as a boy on Sydney's Manly Beach, was the head carpenter for the the tunnel beneath Stalag Luft III.

Within days of emerging from "Harry", he was also one of the 50 escapers who, having been recaptured, were murdered by the Gestapo to appease the mad rage of Adolf Hitler, who had initially wanted every escaper shot.

John Williams and his best mate and fellow flier Rusty Kierath, of Narromine in NSW, and two others – RAF Flight Lieutenant Leslie Bull (the first to escape the tunnel) and Jerzy Mondschein, a Polish Flying Officer attached to the RAF – were stopped by a German patrol as they floundered through the snow into Czechoslovakia a few days after the escape.

After interrogation they were bundled into a car, taken into the forest and shot in the back and in the head. The Gestapo trucked their bodies to the town of Most – then known as Brux, about 80km north-west of Prague – and tossed them into a crematorium's ovens. The SS signed death certificates of the four the day before they were murdered, claiming they died "trying to escape".

Louise Williams, a former foreign correspondent, columnist and foreign editor for Fairfax Media (disclosure: I worked with her at The Sydney Morning Herald for some years) has lived with the knowledge of John Williams since childhood. He was her uncle – her father's brother.

Yet the details of John Williams' life and death, at the age of just 24, floated, like so many stories within stoic Australian families, just out of reach.

Then, in 2001, Louise received an email from a stranger – a Czech pilot interested in military aviation history who had tracked down the final days of her lost uncle.

And so Louise Williams set out to finish for her family a long unfinished business. She would use her careful research and often lyrical writing skills to rescue her father's brother from a Hollywood myth.

She was concerned the life story of a man mythologised by her family might not live up to expectations. Instead, she discovered a young man whose life added up to vastly more than that of a POW, escaper and victim of Nazi murder.

Her newly published book, A True Story of the Great Escape, reveals a complicated, brilliant young man who loved surfing, classical music and books, who vaulted from a working class childhood to a privileged education, thanks to an aunt who never revealed she paid his school fees, and became an early Australian recruit to the RAF: an officer pilot in Britain with war coming.

Along the way – and here is a cautionary Australian story for the ages – he lost his closest boyhood friend, Hans Wicke, to national paranoia. Wicke was Australia's champion board-riding surfer, about to take to the international circuit. Instead, he spent most of World War II behind Australian barbed wire, interned for having been born in Germany. Williams tracked down Wicke, aged 97, one of the many backstories that make her book so deeply absorbing.

In England, repelled by the soft, rich young men of Oxbridge, John Williams turned down a permanent position as flight instructor with the Cambridge University Squadron. Nevertheless, by the age of 20, he was training pilots in the north of Scotland and later, trained Australians to fly in Rhodesia.

He was, thus, among the elite of pilots, with 1000 hours under his belt, when he swung into action against Rommel's forces in North Africa.

At just 23, he was seconded from the RAF to become a squadron leader in the RAAF just before the Battle of El Alamein began. Eschewing a pilot's uniform, he flew more than 100 missions in shorts and sandals, and was awarded the Distinguished Flying Cross for courage.

On October 31, 1942, Squadron Leader John Williams was shot down, far behind enemy lines, by his own confused Number 2 pilot.

He was captured and taken to Germany, where the young man from the air went down a tunnel code-named Harry.

Steve McQueen could barely measure up.

A True Story of the Great Escape, by Louise Williams (Allen & Unwin). $29.99