Their eyes were straining by the time they got through the last page of listings, but they’d ended up with three numbers that looked hopeful and Henderson jotted them down before replacing the directory on its shelf and stepping up to the operator. She didn’t look comfortable with the black uniform and Marc’s bloody face.

‘How are we doing?’ Henderson asked, in French.

‘It’s difficult,’ Marte explained, as she pointed to her tall console filled with connection sockets and dangling wires. ‘Normally, a connection to Tours requires only two links, via the exchanges in Le Mans and Tours. But Le Mans was damaged in a Boche air raid last night and …’

The word Boche was offensive to Germans and Marte turned white as she looked around at Henderson. ‘I mean … a German air raid, sir. Now we have to route calls to Tours via Dijon, Lyon and Bourges. With the network so busy and many lines damaged by bombing it can take a very long time to contact the various operators and establish a long-distance connection.’

‘I see,’ Henderson said. ‘Where are we now?’

‘I’m waiting for the operator in Dijon. She’ll contact me as soon as she has a line available to Tours.’

‘Can you tell them it’s important?’ Henderson said.

Marte shook her head. ‘They know Paris is occupied and there’s a risk they’ll cut us off. Operators in some towns have stopped connecting our traffic.’

Marc and Henderson waited while the operator continued her business, answering calls and moving wires across her console from one plug to another. Henderson was nervous. He had no idea how good the Germans’ radio communications were, but it could only be a matter of time before every soldier in Paris was on the lookout for a man and boy who’d stolen a Gestapo uniform and a motorbike with sidecar.

After fifteen anxious minutes, a white light flashed above the word Dijon on the console. The operator plugged in a jack and picked up her handset.

‘I see,’ she said sadly. ‘Thank you for trying, Elène.’

The operator turned towards Henderson. ‘I’m sorry, Major. The operator in Dijon says she can’t find a line.’

Henderson looked around to make sure that the German engineer was out of sight. ‘I’m not really Gestapo,’ he confessed. ‘I’m a British agent and we need to get out of here before we’re caught. If I left you a message, is there any way that you might try again later and pass it to one of these numbers in Tours? The lives of two children are in danger.’

The operator looked sceptical, suspecting that this was a Gestapo trick to test her loyalty. She spoke in broken English. ‘If you are an Englishman, I assume you can understand what I am saying?’