Later that morning, Cooper found himself watching a man in a grey sports jacket approaching a cash machine outside Somerfield’s supermarket. Running his finger along the edge of the card slot, the man glanced over his shoulder with an apologetic smile. He wasn’t sure whether he liked being watched or not.

There were two ATMs at Somerfield’s, both set into the outside wall near the trolley park, about fifteen yards from the main entrance. A small queue of shoppers had formed at the other machine, fidgeting with their carrier bags and purses.

‘If you feel an obstruction of any kind, don’t use it. That’s the best advice. Usually there are a couple of tiny prongs. Here, see?’

With a flick of the finger, the man pulled out a thin, clear sleeve of rigid plastic. He held it up to reveal a loop at the back.

‘This is the old Lebanese Loop trick. The loop retains a card when it’s inserted. Since the machine can’t read the magnetic strip, it keeps asking you to re-enter your PIN. Someone standing behind you watches you tap your number in. When you walk away, the suspect removes the card and empties your account. Bingo.’

‘Surely that type of device is easy to detect?’ said someone in the watching group. ‘We just saw you do it.’

‘But I know what to look for.’

PC Steve Judson had greying hair, a little longer than favoured by most police officers. He worked with the Plastic Crime Unit, a team struggling to deal with a mounting wave of cash and credit card fraud. According to the latest figures, it was big business – worth at least forty million pounds a year across the country.

Judson looked at the queue for the adjacent cash machine. ‘This is a typical location. The ATMs would be more secure inside, but the store isn’t open twenty-four hours. Some customers want to use them late at night, when this car park is probably deserted.’

‘Is that when the biggest risk is, rather than when the cash machines are busy?’ asked a female DC, one of two who’d driven over the hills from B Division for the plastic crime session.

‘The risk is different. If you look at the people in the queue there – they’re close enough to each other to make shoulder surfing easy. But at night, when the place is empty, you’d be pretty damn suspicious of somebody who came and peered over your shoulder, wouldn’t you?’

There were other officers present in the car park who’d come from Nottinghamshire and even from Leicestershire. Strangers, but probably future colleagues. No one was talking about their future this morning, but it must have been in everyone’s minds when they greeted each other.