It took them just six minutes to get to Vauxhall House, zipping through any red lights with the siren on and the bike’s lights flashing. The bike pulled up outside with its siren still going. Shepherd took off his helmet, gave it to the motorcycle cop, and ran to the main entrance. Charlotte Button was there waiting for him, dressed in a dark blue suit and a pale blue shirt. ‘You made good time,’ she said. ‘Now do you want to tell me what’s wrong?’

‘Let’s have a look at the satellite photographs,’ said Shepherd. ‘There’s a chance that I’m wrong.’

‘Wrong about what?’

‘The clock’s ticking, Charlie,’ said Shepherd impatiently.

They both showed their MI5 ID cards to a blue-blazered security guard and walked through a metal detector arch manned by two more men in blazers. ‘I’ve got us an operations room on the fourth floor,’ said Button. ‘And I’ve got a few other people there just in case we have to move quickly.’

‘If I’m right, we will,’ said Shepherd.

Button swiped her ID card through the sensor in the lift and it took them smoothly up to the fourth floor. As soon as the doors opened Button led Shepherd down the corridor to a room with two double doors that had been left open. Shepherd could see six men sitting down facing half a dozen large LED screens on the far wall. All the heads swivelled as Button and Shepherd walked in. Only one of the men was wearing a suit, the rest were in casual clothing, and one man in his thirties looked as if he had come straight from his garden, in a baggy green sweater with brown suede patches on the elbows, and threadbare corduroy trousers with damp stains on the knees.

‘Gentlemen, apologies again for getting you all here on a Sunday but we have something of a situation. What that situation is I’m going to leave it up to Dan Shepherd to explain. Dan, over to you.’

Button stood with her back to the wall and folded her arms as Shepherd walked over to one of the female technicians and pointed at the photograph of the Athena, docked at Southampton. He pulled out the photograph that he’d ripped from the Sunday Times and gave it to the technician. ‘Can you blow this up and put it on one of the big screens, and then give me one of the satellite photographs on the screen next to it?’

The technician nodded, scanned the photograph, and tapped on her keyboard. The Sunday Times picture filled the left-hand screen. A few seconds later there was a second picture of the Athena, taken from overhead, on the screen on the right.

‘OK, so on the left is the Athena docking at Southampton,’ said Shepherd. ‘On the right is the ship at sea, just after it was taken by the pirates.’

Button looked at both screens and shrugged. ‘I don’t see it,’ she said.