A few years ago, I received a letter from the past.

The single sheet of crumbling yellowed paper was dated Mother’s Day, May 14, 1944, and covered — unmistakably — in my grandmother’s handwriting.

The original envelope, likewise tattered by time, had been carefully addressed to Australian Prisoner of War No 838.

It’s almost 73 years since my grandmother lovingly sealed that same envelope and mailed it off to her eldest son John.

He was, she had thought, incarcerated in the Nazis’ supposedly ‘escape proof’ camp for Allied air force officers, Stalag Luft III.

But in those days of military censors and sea mail, news from behind enemy lines travelled slowly. By May 1944, as the Allied forces began to scent a Nazi defeat, John was long gone. And, eventually, the letter was lost.

My grandmother could not possibly have imagined that six weeks earlier John had crawled out of the now famous secret underground tunnel out of the camp, in what has since been known as the Great Escape.

Nor that John had made it, disguised as Czech worker, over the mountains and out of Nazi Germany, trudging in waist-deep snow with fellow POW and former Sydney schoolmate “Rusty” Kierath.

I am grateful that as she signed off with her prayers, she did not yet know of her son’s fate.

How pieces of the Great Escape puzzle fell into place

John was my dad’s eldest brother, so I grew up with the story of the Great Escape, and his role as chief carpenter on that extraordinary feat of engineering and subterfuge.

By any measure, it’s a fantastic story — a David versus Goliath tale, a triumph over (extreme) adversity and a tragedy, all rolled into one.

But the Hollywood blockbuster, featuring Steve McQueen, so thoroughly Americanised the escape — even though not a single US airman took part — that John’s story, and that of the other five Australian escapees, always seemed just out of reach.

No-one had ever pieced together John and Rusty’s incredible trek, nor solved the mystery of their final hours. So, about five years ago, I began to investigate in earnest.

Foreign Correspondent came along on my first trip back to Stalag Luft III, just as the first pieces of the puzzle were falling into place.

A Czech commercial pilot and amateur historian, Michal Holy, had found a key original Nazi document in the Prague archives, by sheer chance.

It had fallen out of a manila folder when he was looking for something else. Realising its importance, Michal had tracked my family down on the other side of the world.

One document led to another. Remarkably, too, several people were still alive, including John’s surfing buddy from the early days on Manly Beach and one of the group of 10 POWs John had led out of the tunnel.

With my sister Megan’s help, I set up camp in London temporarily and we commuted out to the National Archives daily to wade through huge piles of declassified files, filled with both fascinating and tedious details of virtually every aspect of WWII.

But Stalag Luft III and the escape warranted its own series of files.

Without the aid of a digital search function, it was a matter of just reading and reading more; until we stumbled over John’s name, usually as part of someone else’s story.

The Nazi bureaucracy gives itself away

It took a couple of years, working on and off, to finally piece the picture together and to turn it into a book.

What was so remarkable was the sense of humour that had prevailed in the camp. The life the POWs had built for themselves was so rich, with their sports carnivals, plays, classes and their endless efforts to confuse their guards, that it shielded the underground digging from view.

Engrossed, it was easy to forget how the story ended.

But among the blizzard of detail, there were three single pieces of paper that really stood out. Documents so deeply personal the Hollywood myth finally gave way to a family tale.

What Michal had stumbled across was the original Nazi cremation order listing John, Rusty and their two companions. The Nazis had claimed they had been recaptured inside Czechoslovakia and then shot while trying to run away. But, the document was signed the day before their deaths.

Everyone knew the Nazi executions of 50 of the 73 Allied POWs recaptured after the Great Escape had been clinically planned. Here, all these years later, was the paper trail.

The second find was so unnerving I couldn’t help thinking back to my first visit to Cambodia as a foreign correspondent in the late 1980s, just after the Khmer Rouge had been driven out.

That murderous regime had filed away thousands of blank-faced photos of their victims, the last images taken before their executions.

It was a haunting enough experience then. I remember wondering how it might feel to know any of the people in those terrible photos.

In a folder in London, we came across the Nazis’ last images of John and Rusty, looking out at their inevitable fate.

Letter ‘at last, returned to sender’

Then, there was my grandmother’s last chatty, loving letter to John. With touching diligence, the Allied postal service had sent it on to the RAF in India, just in case he’d been reposted.

Then, I understand, it finally made its way back to Australia to the family, only to be accidently thrown out when the box it was packed in was damaged in a flood.

But as it turned out it wasn’t lost forever at the tip. Someone had picked it up and had recognised the name of the POW camp.

He thought it might be important, so put it safely away for many years. When the Foreign Correspondent segment was first shown, he realised what he had found.

On a sunny autumn Sydney morning, I went out to the letter box to find a crisp, clean envelope with these words on the back: “At last, returned to sender, Kind Regards”.

Inside was that last frayed letter, filled with the intimacy of ordinary, family news from a mother missing her son on Mothers’ Day, and concluding: “With love and prayers, beloved son, may angels guard thee.”

Louise Williams is a Sydney writer and editor. She is the author of A True Story of the Great Escape, published by Allen and Unwin.

Watch Foreign Correspondent: The Real Great Escape on ABC TV at 9:30pm.

This post originally appeared on ABC News.

Featured image: Steve McQueen in The Great Escape, Getty.