Martin was a small, undersized man with prematurely white hair, but his arms and shoulders were over-developed from a spell of working in the rock quarry at Dartmoor and he lay on his side and swung vigorously with a seven-pound hammer at the cold chisel which Fallon held in position.

When the wall gave, it was not one, but a dozen bricks which collapsed suddenly into the cellar on the other side. Martin grinned, his teeth gleaming in the light of the lamp.

‘There’s present-day British workmanship for you. I don’t know what the country’s coming to.’

Morgan shone his lantern into the darkness on the other side and picked out the control panel at once. ‘Come on, let’s get in there,’ he said. ‘We’re right on time. Let’s keep it that way.’

It was the work of a couple of minutes to enlarge the hole sufficiently to allow him to pass through and he left the others to manage the equipment and made straight for the control panel.

There were thirty-seven boxes on the board, each one numbered, and he had to pull the switch on nine of them. He had memorized the numbers, but checked them from the list Vernon had given him just to make sure.

‘Everything okay?’ Martin said at his shoulder.

‘Couldn’t be sweeter.’ Morgan dropped to one knee, located the green cable running along the edge of the skirting board and severed it neatly with a pair of pocket cutters. ‘That’s it unless Vernon’s made a mistake somewhere, which I doubt.’

When he opened the door, the outside corridor was brilliantly lit by neon light. ‘What in the hell is the idea of that?’ Martin demanded.

‘For the television cameras, you fool. They wouldn’t see much in the dark, would they?’ Morgan led the way out into the corridor and grinned tightly. ‘Keep your fingers crossed. If that bloke upstairs is still awake, he’s seen us already.’

‘I can’t see any cameras,’ Martin said in bewilderment.

‘No, but they can see you.’ Morgan paused at the foot of the service stairs. ‘You stay here. Jack and I will go and take a look.’

He went up the stairs quickly. The door at the top had a Yale lock and therefore opened from the inside with no difficulty.

The hall was tiled in black and white and brilliantly illuminated, its great glass doors protected by a bronze security grill. Morgan knew exactly where he was making for. He crossed the hall quickly, found the third door on the right with Control Room painted on it in black letters and turned the handle gently.

The guard had obviously tumbled from the black leather swivel chair in front of the control panel and sprawled on his face. The thermos flask stood open on a small table at one side and Morgan poured a little into the empty cup and tested it.