Meanwhile, just across the border, Nottinghamshire had become the first force in the UK to have armed officers on routine patrol. In parts of Nottingham, officers were issued with Walther P99 pistols, just like the one James Bond used, and had Heckler and Koch semi-automatic carbines in their patrol cars for back-up.

And that was before September eleventh and July seventh, and all the other landmark dates of terrorism. Cooper found the development worrying, an ominous sign for the future of policing in this country. But he couldn’t ally himself with the Palfreymans of the world, either.

‘Yes, I do have the training to spot a liar,’ said Fry as they walked back down Palfreyman’s drive to the car.

‘I’m sure you do, Diane,’ said Cooper.

‘I know all the indications to watch for.’

‘You don’t need to tell me. You know David Palfreyman was just trying to wind you up back there, don’t you?’

‘Bastard.’

Cooper looked across the road. ‘Hold on a minute, Diane. I won’t be long.’

‘Where are you going?’

‘There’s a Range Rover parked at the Brindleys’ house. Is it theirs?’

‘Yes, I think it’s Mr Brindley’s. Why?’

‘It’s a TD model.’

‘So? You’re not that interested in cars, Ben.’

‘Do you know what TD stands for, Diane? It means Turbo Diesel. I want to ask Mr Brindley if he’s ever been offered cheap illegal fuel.’

When Cooper came back, Fry was sitting in the car, still fuming.

‘They’re called the Ten Signs,’ she said. ‘Lack of eye contact, a change in the pitch of the voice, clearing the throat. And then there’s the body language – tapping the foot, fidgeting with the hands, blinking too much.’

Cooper got behind the wheel. ‘Turning the head or body away, changing the subject, attempting to deflect questions using humour or sarcasm.’

Fry looked at him. ‘Have you done the same course?’

‘Er, I sort of picked it up on the job,’ he said, trying not to sound too much like Palfreyman.

‘What did Mr Brindley say?’

‘He’d never even heard of illegal diesel.’

Fry watched the landscape going by as Cooper drove over the plateau towards Edendale. On the highest points, the drizzle and mist became almost indistinguishable from low cloud, and Cooper had to put the headlights on. Spray from passing lorries made visibility even worse.

‘Ten Signs,’ said Fry. ‘Put all those techniques together, and only a really good actor can get away with an undetected lie. And PC David Palfreyman is not that good an actor.’

Back at the office, they found DCI Kessen in the CID room with Hitchens. He had put in an appearance from his other major enquiry and was catching up on progress.

Kessen studied Fry as she entered the room.

‘Ah, DS Fry, glad you could join us.’