Last Sunday, I became the first Englishman to check in at Colditz castle since 1945. And then I did what any Englishman with a bit of pluck would do next: I waited for the cover of darkness and escaped.

As an exercise in sheer pointlessness, this might seem to be up there with modern jazz and telling children to be quiet, but bear with me. When you know the circumstances, it might make sense. The circumstances are these.

Colditz was the most notorious PoW camp of the second world war. The Wehrmacht declared it escape-proof; the allied inmates proved them fulsomely wrong, staging a string of break-outs so daring and audacious that they inspired a film, a TV series, even a board game. In short, it’s a British icon, a part of our heritage that just happens to be marooned in Saxony.

Now the castle that was once intended to stop foreign guests leaving is inviting us back — this time on a voluntary basis. Last week, in a move that is bound to spawn a thousand “This place is like a prison camp” gags, they opened a youth hostel inside the castle walls. This I had to see.

And, of course, escape from.

It had occurred to me that the youth hostellers had opened up an intriguing possibility. If they let you stay in, it meant you could break out. What better tribute to the heroes of my youth than to follow in their surreptitious footsteps?

What I didn’t anticipate was being part of one of the biggest mass escapes the castle has ever seen. But more of that later.

COLDITZ CASTLE is huge, a hodgepodge of buildings constructed over 500 years. The 34-room hostel is in a 19th-century portion that housed the Kommandantur, the German garrison’s wartime HQ. Not much for nostalgics here: with ruthless efficiency, the government of Saxony has restored the original facade, but rebuilt the inside from the bottom up, and all traces of its previous character — of any character, come to that — have been expunged. It’s modern, clean and efficient. It’s also slightly shocking, as if they’d plonked a Travelodge inside the Tower of London.

That hardly matters, though, because most of the castle is gloriously unrestored. Of the mind-boggling 680 rooms, most of them temptingly out of bounds, many still bear the scars of those wartime escapes. I joined a guided tour with the erudite Renate Lippmann. Smile very nicely and, as well as the public exhibits (escape tools, rope ladders, provisions and so on), she’ll lead you round some off-limits scenes of the castle’s celebrated break-outs. I wanted to marvel at the inventiveness and audacity of those escapes — but, more than that, I wanted to learn from their example. For me, this tour was going to double as a recce.

We climbed the old spiral staircase to the theatre, scene of many a PoW production (they involved a disturbing amount of cross-dressing) and launch pad for the first British “home run”: Airey Neave hid under the stage before carving a hole through the floor (still there, by the way), chucking on a fake German uniform and strolling out past the guards. Tempting, but I didn’t have time to run up a youth-hostel polo shirt.

Renate showed us the attic where the Colditz glider was built, a full-sized two-seater secretly assembled by two British pilots. Nope — paper planes are my technical limit. Then there was the wine cellar and chapel, where the French dug a mazy 140ft tunnel that snaked under floorboards, through solid rock and into the castle’s foundations. A classic well worth emulating — but the spoon I’d brought for digging wouldn’t be up to the task.

Finally, beyond a maze of security fences and “keep out” notices, she allowed us into the small cellar from where Pat Reid, master escaper, and three fellow officers squeezed and scrambled their way to freedom through a tiny air vent 9ft above the floor. Bingo! This one I could handle. All I’d need would be the cover of darkness and some accomplices to help with a leg-up. BY 3AM, I had both. Andy Russell and his pals were Colditz enthusiasts on a long weekend, staying at a hotel nearby. We met that evening in the town, having discovered a mutual interest in the local brews. (Don’t knock it: bonding over a bevvy is a British tradition around here. The inmates used makeshift stills to produce hooch out of raisins. It turned their teeth brown, though.) A plan was developed. Andy and co would sneak in under the castle’s back gate — we’d already spotted a good 8in gap — and we’d rendezvous at the cellar. The objective: no disturbance, no damage. Like our role models, we’d go undetected. We’d better. If the nightwatchman nabbed us, I anticipated a severe sense-of-humour failure.

One by one, we stole across the moonlit cobbles, slid around fences and boards, then crept to the cellar. The vent was even higher and narrower than it had looked by day. Reid had been forced to strip naked to squeeze through. We’d try to do it decently: the popular press were kinder then, and we could see “nude vent orgy” headlines looming. Andy, an ex-soldier and a natural leader, took off his jacket, got a leg-up from Ian, and went for it.

Well, it wasn’t easy. We were in that cellar for more than an hour. Dave, in particular, had a hard time, stuck fast for 20 minutes; for once, I was grateful to be a skinny beggar, sliding out in 60 seconds. Finally, with pushing from below and pulling from above, six Englishmen had emulated Pat Reid — if you can compare evading 150 armed guards and crossing hundreds of miles of hostile territory to evading one bored nightwatchman and getting a Ryanair flight back to Stansted. Which, of course, you can’t.

IN THE MORNING, I went to check out, and Herr Steinbach, the hospitable manager, took my key. After a chat about the hostel, I slipped in the question I’d been leading up to. Wasn’t he concerned that his British guests might try to escape?

He looked nonplussed. “But . . . ” he mumbled, holding up the wooden fob I’d just surrendered, “ . . . you have a key, you see.”

While the modern Germans are an admirable nation, from whom we could learn much, make no mistake: there is still a gulf of understanding between us. Herr Steinbach is right — hostel guests can come and go as they please — but if he thinks his British guests won’t at least be tempted to Escape from Colditz, he’s got another think coming. Keys? As our American allies would have said, keys are for wimps.

Travel details: Colditz Castle youth hostel (00 49 351 494 2211, www.djh-sachsen.de) has rooms from £17pp, B&B (£15pp if you’re under 26). Tours of the castle cost £4.75. Ryanair (www.ryanair.com) flies from Stansted to Altenburg, 40 minutes’ drive away. Europcar (0870 607 5000, www.europcar.co.uk) has three days’ car hire from £95.