The general gave a sharp laugh. ‘The German boy heard him speaking to Benedict in German. That’s proof enough.’

‘Yes, sir, but the German boy is supposed to be dead. We faked an execution. We broke army rules. Even a general could be in deep trouble for that... General.’

The officer rubbed a troubled hand over his moustache. ‘So what do we do? We can’t let Grimm get away with it... and go on stealing more secrets.’

‘No, sir, but the important person in all this is really Benedict.’

‘And we have no idea who he is?’ General Bruce asked.

‘No, sir. We just know he is somewhere near the front line, close to the enemy. He can pass messages across to them. We need to stop him.’

‘But we don’t know who he is.’

‘That’s why we still need Sergeant Grimm. He can take us to him. Let’s give Grimm plans for the Whippet tank and see where he leads us.’

‘And the weakness? We can’t tell the Germans that gas will stop the tanks. It may just get through.’

‘No, sir, we’ll invent something. The Germans use flame-throwers...’

‘Evil weapons.’

‘Yes, sir. Let’s say the tanks will explode if the enemy uses flame-throwers.’

‘And will they?’

Captain Ellis almost smiled. ‘No, sir. And any enemy trooper with a flame-thrower would have to get closer than ten yards to spray a tank. He’d be shot before he got within fifty yards.’

General Bruce looked troubled. ‘So we need to feed Silver Hand with more fake secrets – tank drawings he can’t read down the phone – and watch him run with them. You’re sure he’ll lead us to Benedict?’

‘Yes, sir.’

The general lowered his voice. ‘And the German boy – the one we failed to shoot? He could cause us a lot of trouble.’

‘Send him back to Germany, sir.’

The general sat up straight at his desk. ‘Arrange it, Captain Ellis. Arrange it.’

‘Send a German soldier back to Germany? It may be tricky.’

The general sighed. He took a printed sheet of cream paper from his desk. ‘This is a free pass, signed by me. No one may stop or question the person carrying this. He could walk into Buckingham Palace with it.’

Captain Ellis took the paper, folded it and tucked it into his jacket. He stepped back and saluted smartly. ‘Young Marius is as good as in Berlin right now, sir.’

But of course he wasn’t...

26 August 1918: The Fletcher farmhouse, Bray

The smell of the smoke from burned Bray still hung in the air. Canadian soldiers repaired some buildings to make garages for their lorries and tanks. They sounded more cheerful now they were moving forward. Their songs hung in the bitter air...

‘The general gets the turkey, the colonel has his duck;

The officers have poultry, they always were in luck;

The sergeants have bread and cheese and mop up all they can,