But Birch’s car must have been missing for at least a few hours before he picked up the phone. Why would that be the case?

When Naylor comes in, Hagen gives her the full run-down: the cash deposits in Birch’s accounts, the switched-off phone, the mismatch on the stolen car timing.

‘Great work, Brad,’ she says. ‘If we can get the guys who nicked it on CCTV, we might get an ID and start to really put things together. The bad news is, I think you should go up there.’

‘To Hartlepool? No worries. My nan lives near there. She’ll be pleased to see me.’

‘It’s a long drive. You’d better take the train, or you’ll be gone for days. I’ll talk to Campbell and tell him what’s going on so he can authorise it. Make contact with Cleveland before you go, tell them you want to look at any CCTV footage they can get hold of for that location on that date, and see if they can dig out details on the call reporting the vehicle stolen. Allelujah, we might be making progress here at last.’

Cleveland Police Headquarters is an anomaly of a building, a modern, red-brick fortress amongst the vintage buildings of old Hartlepool – the Masonic Hall (now a tea-room and wedding venue), the Town Hall theatre, the Engineers’ Club and Snooker Room. Hagen announces his business and signs in, and waits in the reception area only a few minutes before a plain-clothes officer about his own age comes to greet him.

‘DC Alex Heron,’ he says. ‘Pleased to meet you.’

‘Pleasure,’ says Hagen, and here amongst friends, already his accent is lapsing further into its north-eastern origins.

‘We’ll take the stairs,’ says Heron, leading the way. ‘You’d wait all day for the lift.’

They pick up coffee from a machine, and in an open-plan office almost identical to the one he’s left in Berkshire, Hagen pulls up a chair to Heron’s desk.

‘So, you know what I’m after,’ he says. ‘This is all connected to the Ferrers case, the abduction.’

Heron shakes his head.

‘A bad business,’ he says. ‘The sooner someone’s doing time for it, the better.’ He has a copy of the original report of the Focus theft and places it in front of Hagen. ‘The theft was reported online.’

Hagen glances over the printout. Birch gave his full name and his address in Chelmsford. The phone number he provided is a mobile, the same one that’s since gone dead.

Heron opens up Google Maps and finds the location of the reported theft: Chatham Road.

‘It’s an interesting one, this. Bearing in mind the seriousness of the offence, we’ve done you a favour and pulled in what CCTV we can find, which has come from some interesting sources. What line did you say the car’s owner is in?’