Manly soldier became a target ... Squadron Leader John "Willy" Williams. In truth, of course, he didn't survive. (The film's characters were composites of the real men.) Willy did play a major role in planning and excavating the tunnels. And, he did make it out of the tunnel and onto a train, travelling with his cellmate and old Shore school friend, Reginald ''Rusty'' Keirath. But the pair were later intercepted slogging their way across the Czech border and were among the 50 escapees executed on Hitler's personal orders. Willy had a reputation as a joker - he flew sorties in the Middle East wearing baggy shorts and sandals - but his letters and family history reveal a thoughtful and serious young man. As a teenager between the wars, he was friendly with a German member of the Manly Surf Lifesaving Club who bragged that a popular Hitler-led Germany would ''sort the Aussies out'' when they landed here. No one much listened. However, Willy did and signed up with the RAF before war broke out, leaving his medical studies to travel to Britain.

Manly surfer. He wrote home every week, often of his dream of surfing at Manly again; but never came back. When an unknown Gestapo officer put a gun to his head in a remote forest on the other side of the world, Willy had been training fighter pilots or flying combat missions since he was 18. He had been credited with four victories and been awarded the Distinguished Flying Cross. Every week of his war, he wrote home. My father, Owen, died almost a quarter of a century ago. When my uncle David, the longest surviving of the five Williams siblings, passed away in 2006, I became the de facto family custodian of Willy's story. But, the thread of memory was broken, there was not a single family member left alive who had known him. Over the years, however, I have collected interviews, letters and anecdotes and, bit by bit, Willy's story has taken shape. In the 1930s, beachside Manly was a sparkling antidote to the harsh reality of the Depression. Like many others, the Williams family was living in reduced circumstances. Grandfather had been a successful architect in New Zealand and was hit hard when spending on public building dried up. By the time the family moved to Manly they were piled into a rented two-bedroom flat a stone's throw from the beach, the older boys happily sleeping on the verandah and grandfather apparently selling off the NZ assets to pay the school fees. The family photos tell a story of a young man who loved life; swam, surfed, rowed, played rugby and studied, enrolling in medicine at the University of Sydney in 1938, age 17. But, he didn't sit the first-year exams; having won one of four places for ''colonials'' in the pre-war RAF pilot officers training scheme, he left for Scotland instead.

It was a war, everybody had problems. In Willy's letters there was always an upbeat tone but he did plead with the family not to let ''the kids'', his youngest brothers, sign up. Likewise, letters from his RAF and RAAF colleagues also describe him playing the clown - except in the air, where he was reputedly a serious and aggressive combat pilot. It seems he took escaping just as seriously. A few years ago, I picked up the phone to the UK and spoke to RAF Squadron Leader Bertram ''Jimmy'' James, then in his early 90s, and suddenly it was all real. ''It was exhilarating. It felt like liberation just to be on the other side of the fence,'' said Jimmy, recalling the moment his group was led out of the tunnel by Willy. It was a feeling he obviously still relished. The fear, extreme cold, fatigue and reprisals could wait.

As chief supply officer for the escape, then head carpenter, Willy was in charge of ''scrounging'' the 4000 or so bed boards used to shore up the 10-metre-deep, 111-metre-long escape tunnel and myriad other materials; all without the guards realising anything was missing. The POW camp was deliberately sited on sandy soil, the most likely to cave in, and its perimeter was microphoned so they had to dig very deep. Willy and the carpenters worked for months in a tiny underground chamber, its entrance concealed under a stove. The escape operation occupied 600 men and aimed to break 200 of them out; the most audacious escape plan of the war. Willy and Rusty were escapees 31 and 32; escape slots were allocated on rank, contribution to the construction and likelihood of success. When I asked Jimmy about their fears - of the claustrophobia of a tunnel barely big enough to accommodate the wide shoulders of a large man, of the cave-ins, stale air and the threat of discovery or recapture and reprisals - he was taken aback. To survive psychologically as a POW life needed purpose. The prisoners in Stalag Luft III were all officers, so they were not required to work, which left some of the sharpest minds and most courageous characters idle to plot, he said. And, escape was a duty, or at least you were expected to try. ''We were just push-on kind of chaps really,'' Jimmy said. Willy was last seen trekking making his way with Rusty on foot through waist deep snow drifts on the border of German-occupied Czechoslovakia, en route, they had hoped, to Switzerland.

The escape so enraged Hitler that he ordered the secret execution of 50 of the 73 recaptured men, in violation of the Geneva Convention. Escapees were driven into remote forests to be shot. I always presumed, and in some ways hoped, that Willy and Rusty died together, probably with their fellow escapee pilots, the British Leslie Bull and Polish Jerry Monshein, also intercepted on the Czech border. All we know for certain, however, is that the four men's bodies were brought in together for cremation in Most. Only Willy had reportedly been told they were not heading for a new prison camp, as the rules of engagement dictated, but were on their way to die. In Sydney, the Great Escape was a ''huge story''. But with no word that Willy had been among the escapees, there was still hope. ''I used to half worship him. Mum was incredibly attached to John [Willy] and had been incredibly affected by him signing up,'' my late Uncle David had told me. When the family finally received confirmation of his death, there was no great outpouring of grief, David said. There was no funeral, no memorial. ''It was a war, everybody had problems. ''It was like the knight who went out in shining armour and then his horse comes back without a ride. It was an ordinary occurrence [in war]. You just kept things to yourself.''

But, the grief, like a dank, invisible fog, settled anyway. My grandmother became chronically ill and like many bereaved mothers of the era she took to attending seances, finding her son back riding the Manly waves through mediums. And she fought a long personal battle to be awarded the Mothers' Medal in recognition of her loss. In the end, she failed, a long string of bureaucrats ruling her ineligible because Willy had been born in New Zealand and had been an RAF officer before being lent to the RAAF's formidable 450 Squadron, the so-called Desert Harrassers. A massive war crimes investigation into the Great Escape murders followed the Allied victory. Twenty Gestapo officers were sentenced to death and many more jailed, but no one was brought to justice for the murders of the Most four. Next weekend, on the 68th anniversary of the escape, a Czech Air Force fly-past and military band will honour Willy, Rusty, Leslie and Jerry with the unveiling of memorial in Most. We, their descendants, will be there. Then, in a hired minibus, we'll make our pilgrimage together, following in their ill-fated footsteps. ''It is something which should have been done many years ago,'' says organiser Michal Holy, a Czech commercial pilot and amateur historian. But why single out these four in a region devastated by the Nazi occupation of World War II and the austere Communist era that followed?

''This was deliberate, calculated murder,'' Holy says, ''not death on a battlefield in war.''