The first thing that assailed Wilde was a smell of damp, burnt wood and rotten vegetation. The antechamber to the complex had been partially destroyed by fire, so the walls were scorched and the guards’ wooden table and chairs were charred.

No one had attempted to clear the place up. It must have looked very like this on May eighth, when the war ended. But why would anyone bother to clean or tidy such a place? Leave it just the way the Nazis left it, a squalid museum to man’s wickedness.

The floor was littered with bits of paper. Wilde picked up a scrap and saw an official heading and, scratched at the bottom, Hitler’s sloping signature.

‘One for your autograph book, Professor?’

Wilde let the paper flutter to the floor. They made their way down concrete steps to a corridor. The light from the hurricane lamps flickered ghostly shapes against the blank grey walls and low ceilings. There were a series of doorways. Minsky indicated one and led him through into a collection of rooms of varying sizes. ‘These ones on the left were used for the telephone exchange and for power generation. On the right, you have a maze of rooms used by Hitler and Eva, his mistress and latterly his wife, though that has never been confirmed to my knowledge. Where is their marriage certificate? Where is the cake?’ He laughed. Wilde merely managed a polite, insincere smile.

The floor here was under a couple of inches of water. ‘It will get a great deal worse when we get heavy autumn rains,’ Minsky said. ‘This part of the bunker is below the water table and there is now no power to pump out the flooding.’

A huge rat ran past Wilde’s feet, its shadow from the hurricane lamp magnifying it into a cinematic monster.

Wilde was trying to imagine the scene here at the end of April. It must have been crowded and claustrophobic with no natural light, dank air, the stench of sweaty unwashed bodies and the encroaching roar of battle outside. The world closing in and all those present knowing that there was no hope of avoiding defeat, whatever their chief might say to the contrary. And with each passing hour, their chances of finding a way through enemy lines becoming smaller and smaller.

There were children, too. The five girls and a boy who were brought here to die by their parents, Dr Goebbels and his wife Magda. What made them think their six innocent babies deserved to be poisoned just because their parents’ lives were about to be snuffed out? That had all happened here, within yards of where he now stood. His stomach churned.

‘My God, this is grim,’ Wilde said.

‘No place to die, eh?’

‘Can we see his rooms – the place he is said to have shot himself ?’

‘Of course. Come through here on the right.’