They continued and the ascent became increasingly hard going. Every quarter-hour they stopped to take water from a flask. At last they arrived at a narrow pasture with towering peaks on three sides, and the hermitage came into view. It was more than Wilde expected. He had imagined a hut, but this was rather more grand – a little whitewashed building made of stone and, beside it, a pretty little chapel, also painted white. Both buildings nestled into the rock face.

A long path of stone steps led up almost vertically from the meadow. Paula Jaeger led the way and Wilde immediately realised it was going to be as tough as she suggested, because there were no handholds, nothing like a handrail, not even a length of rope to grip. One slip and you could do yourself serious damage.

He was already sweating as the morning sun began to burn into the nape of his neck. The air was getting thin and he was breathing heavily, his eyes fixed on the grey stone of each step and on her boots, a couple of feet above him. At the top, he stopped and caught his breath. What now? Why had he even come here? What was he expecting – a cordial welcome from Adolf Hitler in his mountain retreat?

‘You are out of breath, Herr Wilde.’

‘I live in a place called Cambridge – it’s very flat with plenty of oxygen.’ He noticed that she wasn’t even panting.

‘Come on, I will show you around. Though I can’t think what you are hoping to find. If Hitler was here, we would already have been machine-gunned by his SS guards.’

Maybe, he thought. But he took the Walther from his pocket anyway. She walked towards the door of the little house, which was in good condition, with glass windows intact, but he held her back. ‘I’ll go first.’

He pushed open the door and stepped inside a dark hallway. As his eyes adjusted to the gloom, he realised it was the one and only room in the house. The view from below had been deceptive, making it seem a bit larger. A small table with a hard-backed chair backed onto the rear wall and there was a fireplace with ashes in the grate and two blackened pans hanging from hooks. By the door there was a tin washbasin. Beneath the window stood a single bedstead; surprisingly it had a mattress and blankets, crumpled up as though someone had slept here.

And that was it. This was the austere home of the hermits. A place to find God or drive you insane. The strange thing was it still felt lived in. No dust, no cobwebs.

‘Why is there bedding?’

‘For mountain travellers,’ she said. ‘I think someone has been here.’

He turned around. ‘I thought the same. Who?’

‘Someone hiding. I have heard of former SS and Gestapo men concealing themselves in the mountains and forests to avoid internment.’