They were fifty yards up the road past the house when they saw Elder’s green Nissan backing out of his drive, almost before the taxi had driven away.

‘What do we do?’ said Cooper.

‘Has he seen us?’

‘No, I don’t think so. He won’t recognize my car, so long as he doesn’t get a view of our faces …’

Cooper swung into a gateway and turned round to wait. When the lights of Elder’s car went past, he could be seen fiddling with the touch screen of a satnav device attached to the dashboard of his Nissan.

‘OK, Ben. Let’s find out where he’s going.’

Elder drove past Matlock to reach the A6, where the evening traffic from Derby was building up, shoppers and workers making their way home in the December darkness. He turned on to the A610, skirting Ripley and passing right by Derbyshire Constabulary headquarters before crossing into Nottinghamshire. Four miles further on, his car joined the M1 motorway at Junction 26, heading south.

‘He could be going anywhere,’ said Cooper. ‘We don’t want to end up in London for the night.’

‘We’ll see,’ said Fry. ‘I don’t think he’ll be going that far.’

She didn’t have to wait long to be proved right. Elder’s Nissan didn’t even make it as far as the next junction. After a couple of miles, he started indicating left and turned into the brilliantly-lit surroundings of the service area at Trowell.

‘Pass on our location, Ben,’ said Fry. ‘You know the drill.’

Cooper contacted the Nottinghamshire control room to alert them to the presence of Derbyshire officers conducting an operation on their territory. Meanwhile, Fry called Gavin Murfin and asked him to rendezvous at the service station. He was only a couple of miles away, keeping in touch with their location.

‘Why do we need Gavin?’ asked Cooper.

‘We might have two vehicles to follow when we leave here.’

‘I see.’

They watched Elder park up in front of the amenities building where there were some free spaces. At least the area was well lit for security, otherwise the gathering darkness would have defeated them. Cooper found a spot as near to the exit as he could get while still having the Nissan in sight. Then they sat and waited for something to happen.

‘He doesn’t know Gavin,’ said Fry. ‘So he should be able to get nearer to the Nissan when he arrives.’

Cooper looked around the parking area and the buildings beyond it. If he had to imagine a place where no one belonged and everyone was just passing through, this would be it – a motorway service area. The ultimate nowhere land.