Denis Avey, even at the age of 91, cuts a formidable figure. More than 6ft tall, with a severe short back and sides and a piercing glare, he combines the pan-ache of Errol Flynn with the dignity of age. This is the former Desert Rat, who, in 1944, broke into -- yes, into -- Auschwitz, and he looks exactly as I expected. He removes his monocle for the camera, and one of his pupils slips sideways before realigning. It is a glass eye. I ask him about it. He tells me that in 1944, he cursed an SS officer who was beating a Jew in the camp. He received a blow with a pistol butt and his eye was knocked in.

If Avey's story is difficult to believe...

...Avey was a troublesome prisoner. In the summer of 1943 he was deported to Auschwitz, in Poland, and interned in a small PoW camp on the periphery of the IG Farben factory. The main Jewish camps were several miles to the west. "I'd lost my liberty, but none of my spirit," he says. "I was still determined to give as good as I got."

But he knew immediately that this was a different order of prison. "The Stripeys -- that's what we called the Jewish prisoners -- were in a terrible state. Within months they were reduced to waifs and then they disappeared. The stench from the crematoria was appalling, civilians from as far away as Katowice were complaining. Everybody knew what was going on. Everybody knew."

Remarkably, Avey was able to think beyond the war. "I knew in my gut that these swine would eventually be held to account," he says. "Evidence would be vital. Of course, sneaking into the Jewish camp was a ludicrous idea. It was like breaking into Hell. But that's the sort of chap I was. Reckless."...