‘What I don’t get,’ Perry eventually said to Gillard, ‘is how Halliday managed to get his own Mitsubishi Warrior stolen, yet still have it to run you down a few days later.’

The DCI accelerated hard to pass a slow lorry. ‘My guess is that he arranged for your daughter to steal it, in disguise. Then in his witness statement, which of course nobody would challenge, and the CCTV kind of confirmed, he described seeing some bloke driving it off.’

‘But what on earth is the point of something so elaborate?’

‘All right, imagine he just picked up Beatrice Ulbricht at the bus stop on Sunday, attacked her in the Warrior, maybe made some kind of mess in the car, blood, semen whatever. All the forensic leads are going to point back to him, right? He’s sharp enough to know that even if he scrubs it well, there are going to be traces. So his best protection is to have a fallback position in case the car is identified, and that fallback position is that yes, the vehicle is his, but it was stolen from him before Beatrice was killed. So of course it’s got his DNA in it. It’s kind of brilliant really, making himself the victim. Because his is the only description we have, and it is one we are going to trust. After all, we’ve all seen him fall on his arse in the road.’

‘Well, it did look real.’

‘I’m sure it was. I can’t imagine he expected Vanessa to pull him off his feet like that, though I’m guessing that he exaggerated the extent and duration of his injuries.’

‘Vanessa passed her test first time four months ago, but she’d have needed coaching on a big truck like that.’ Perry thought for a moment. ‘Look, I used to be a physics teacher. There’s no point arranging to have his Warrior stolen on the Monday, say, if he killed Beatrice on Sunday. He can’t go back in time and fix it.’

‘Yes, but the marvellous service that Vanessa provided for him on the train was to make Beatrice appear to be still alive two days after she actually died. It’s a kind of timeshift.’

Gillard looked at Perry, who was staring out of the window. It was clear he wasn’t thinking straight, but that was hardly surprising. His whole life had been turned upside down. Not many people could recover from that.

The next day

An early morning incident room meeting saw DCS Rajinder Otara reveal the results of the CSI investigation of Kyle Halliday’s lair under the railway arches. Gillard was aware of most of the main points: that Yvonne Fairfield’s body, already frozen for some years, had been the decoy inside the Mitsubishi Warrior, with Sam bound and gagged inside a locked metal box in the inspection chamber underneath. But some details had eluded him.

‘Here is the Japanese tuna freezer,’ Otara said, pointing to a photograph of a very large cabinet freezer. ‘It’s in this, we are convinced, that the bodies first of Jane Morris, then Yvonne Fairfield and later of Beatrice Ulbricht, were stored. By the time CSI got to look at it, it was clear this freezer had stopped working.’