As Henderson grabbed the phone, the laundress walked over to a clothes rail and grabbed a set of pressed overalls. ‘You’d better put them on,’ she said. ‘If the floor manager catches you in a public area without a uniform he’ll go spare.’

Then the woman looked at Marc. ‘We’ve never had a boy shoe-shine before. The only thing I’ve got that will fit you is a messenger’s uniform. But don’t go getting polish on it because it’ll never come out of white cuffs.’

‘Thank you.’ Marc nodded to her as he grabbed the hanger. His uniform comprised a white shirt, black trousers and a velvet waistcoat with gold buttons.

‘Very fetching,’ Henderson teased, as they stepped back into the corridor.

‘Did you get the room number from reception?’ Marc asked.

‘Six-one-two,’ Henderson replied. ‘Now we need somewhere to put these clothes on.’

They headed back upstairs and passed a janitor’s cupboard that was big enough to change in. Henderson closed the door behind them, switched on the light and unzipped the bag, taking out the compact machine gun and showing Marc how to take off the safety catch, fire and reload. On the way out, he grabbed a mop, plunger and bucket.

‘Now we’ve got to find the lift.’

The staff area on the ground floor was a warren and it took several anxious minutes of wandering badly-lit corridors until they found themselves near the hotel’s reception desk with the main elevators facing directly towards them.

Several Gestapo officers were returning to their rooms. The lift stopped at the second and fifth floors and on each the departing officers were saluted by two German infantrymen on guard duty.

‘Seems they’ve got this place sealed up pretty tight,’ Henderson said.

They were alone for the final ride to the top floor and Henderson used the opportunity to check that his silenced pistol was ready to fire.

‘You sure you’re OK with the machine gun?’ Henderson said. ‘Remember to hold it exactly how I showed you or you’ll rip your shoulder off.’

The two guards stepped forwards as the lift doors opened. ‘State your purpose,’ one guard said, in truly awful French.

Henderson began to mumble a convoluted explanation about blocked pipes in room 612 and how the messenger boy’s little arms would be needed to reach behind a sink and undo a valve. Of course, the Germans didn’t understand a word.

‘Blocked toilet,’ the German said irritably. ‘That’s all you need to tell me.’

Henderson nodded apologetically as he walked off with Marc in tow. But after a few steps he realised he’d gone the wrong way and he turned around. Once they’d passed the guards again, one spoke to the other in German.

‘Useless bloody French,’ he sneered. ‘Too much wine. It’s no wonder they lost the bloody war.’