‘No temporary traffic lights, I take it? That would slow the average.’

‘No. They are supposed to turn off the average speed check when there are lights.’

Gillard leaned over, and move the mouse to get the individual camera measurements. The Toyota averaged 48.1 mph between cameras one and two, but only 13.8 mph between two and three.

‘That’s bollocks,’ Hodges said, sitting back in exasperation.

‘No, it’s not. I know that stretch of road. Our suspect stopped somewhere, in the roughly two miles between cameras two and three, and I think I know where.’

Hodges turned round to look up at his boss.

‘If my hunch is right, we will actually get a good look at our suspect.’

An hour later, Gillard and Hodges had on their screens the CCTV footage they had hoped for.

‘I know this is the only twenty-four-hour petrol station in the area,’ Gillard said. ‘Which means it would be the only one open early on a Sunday morning. Remember there was that horrible assault there two years ago? They upgraded their security after that.’

The BP station had a state-of-the-art multiple camera set-up, with footage held on the cloud rather than on disc locally. This meant it was quickly downloadable to police forces once they had a password issued by the company’s duty security officer. Previously it would have taken twelve to twenty-four hours. That was a big difference when criminals were on the move.

It took a few minutes on fast forward to find the moment when the Toyota pulled in. The entrance camera mounted on the front edge of the canopy clearly picked up the registration number, which matched Morag Fairburn’s car. The male driver was wearing a dark jacket or cagoule, partially open to reveal a lighter coloured shirt. The angle of the camera precluded a view of his face, though the gloves he wore were quite distinct. It was, by the camera clock, 8.19 a.m., around an hour after the attack on Mrs Roy. Gillard was holding his breath as he watched the vehicle edge into the far left-hand of the four service piers. He cross-checked the cloud dashboard with its camera map, and clicked on camera nine, which covered the left-hand side of the pier. A message flashed up.

Camera not in service.

‘Shit! It’s not even two years old!’ He switched to camera eight, on the right of the same pier. Fortunately, there was not a single other vehicle in the filling station to hide the view. For all that, the architecture of the pier meant that signage as well as the location of the pumps obscured much of the view. He could see the Toyota’s door open, but there was no angle on anything above waist height. When the door closed, they could see a pair of black or dark blue trainers, with three parallel light-coloured stripes. The dark trousers looked to be loose, perhaps the bottom part of a shell suit, and was torn on one knee.