I was 13, maybe 14, when I stumbled across one of the books that was to loom large in my life.

It was a dog-eared, paperback copy of Paul Brickhill's The Great Escape — the epic true story of the mass breakout by allied airmen from Stalag Luft III, a German prisoner of war camp in World War II.

The story had everything for an adventure-loving teenage boy: hundreds of hardened POWs digging three tunnels beneath a supposedly escape-proof camp, with everything from bed boards to stolen electric wire "requisitioned" for the effort.

The watchtowers at the real-life Stalag Luft III. ( Supplied: IWM (HU 21018) )

On the night of March 24, 1944, 76 men crawled out of one of the tunnels (named Harry) and made their bid for freedom.

Three made it back to England, 23 were recaptured and locked up again, and 50 were executed by the Gestapo, on direct orders from Adolf Hitler.

It was a shattering end to the ultimate boy's own tale.

The secrets of Tom, Dick and Harry

On the 75th anniversary of the escape, I'm delighting in re-reading Brickhill's book (for perhaps the 20th time) and again savouring a story of bravery and ingenuity. One of grim determination in the face of seemingly impossible odds.

On paper, the Germans' plan to put all the repeat-offender escapees in the one heavily fortified camp seemed like a good one.

Dense barbed wire and imposing watchtowers were the surface-level deterrents, while loose, sandy soil and underground listening devices put paid to the shallow tunnels the prisoners had become extremely adept at digging.

Enter Squadron Leader Roger Bushell, or Big X, the head of the camp's escape committee.

Squadron Leaders Robert Stanford Tuck and Roger Bushell (Big X) in Stalag Luft III. ( Supplied: IWM (HU 1605) )

After narrowly avoiding a Gestapo firing squad on his most recent escape attempt, Bushell was determined to inflict a mighty blow on the enemy in the form of a mass breakout unlike any seen so far in the war.

His plan was for three tunnels (Tom, Dick and Harry) to be dug simultaneously, with the aim of hundreds of POWs getting out and forcing the Germans to divert stretched resources to track them down.

What followed was a veritable escape industry that operated under the noses of the camp guards, nicknamed "ferrets" by the POWs.

False identity papers were forged, air force uniforms were converted into business suits, and German language lessons abounded.

A map of Stalag Luft III shows the location of the escape tunnels. ( Supplied: Ley Kenyon )

All the while, the digging continued.

The dirt was dispersed in attics, and casually spread on the camp grounds through bags hidden in the prisoners' trousers.

Seven tense hours

In September 1943, disaster struck when the guards discovered tunnel Tom.

All efforts were then concentrated on Harry, and by late March, 1944 the 102-metre tunnel was complete.

The night of the escape provided one final element of drama: the tunnel fell several metres short of the thick woods where the exit had been planned (a massive surveying error).

A diagram of the Harry tunnel where the prisoners escaped. ( Supplied: Ley Kenyon )

What followed were seven tense hours of the escapers gingerly climbing out of the hole, a stone's throw from a guard tower, and shuffling across the snowy ground to cover.

Just before dawn, their luck ran out when a stunned guard almost fell into the tunnel.

The jig was up, but not before 76 POWs had fled into the night.

And this is where the celebrated 1963 film dramatically parts company with what really happened.

More fiction than fact

There was no hair-raising theft of a German fighter plane for an aborted flight to Switzerland, and the daredevil Steve McQueen character trying to leap to freedom on a motorcycle was a complete fiction.

The escape routes were much more mundane and low-key, mainly involving cross-country hikes under cover of darkness.

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A nationwide manhunt rounded up all but the three who made it home, and a furious Hitler initially ordered they all be shot. Talked down by his Nazi lieutenants, he settled on the figure of 50.

Over the next few weeks — again, unlike in the movie — the marked men, including five Australians, were taken out in pairs and small groups and gunned down by Gestapo agents.

It was, in the end, a huge price to pay, and decades down the track several escape survivors were still expressing doubts whether the effort was really worth it.

Now, 75 years later, we remember all of these brave men, particularly those who paid with their lives.

The anniversary is unfolding with a touch of sadness with the death over the last month of the last two known Great Escape survivors.

Former Squadron Leader Dick Churchill, one of the handful to be recaptured and sent back to captivity, died at the age of 99.

Jack Lyon, a former RAF navigator who acted as lookout on the night, made it to 101.

The escape veterans may now be gone, like so many of those who fought in World War II, but their heroic exploits live on.

And, nearly 40 years since first picking up Paul Brickhill's book, I am still entranced by the greatest escape of them all.