Back at Mount Browne, after a well-earned breakfast, Gillard sat with Colin Hodges once again going through the CCTV footage. Kirsty Mockett had mentioned three parked vehicles on the southern edge of Ashtead Common as she began her run a week ago, and Hodges had got two of them within five seconds of footage from the Network Rail camera. A white Toyota Avensis estate passed over the crossing just two vehicles behind Mrs Roy’s green Jeep Cherokee. However, the camera was designed purely to monitor the level crossing, and simply caught a passenger side view of northbound vehicles. Nothing could be seen of the driver, nor of the registration number.

‘He could be following her,’ Hodges said. ‘If it’s him.’

Gillard nodded. ‘Have you got it on its return journey?’

‘We’ve got several white Toyota estates going in the right direction up to noon on that day, one was an Estima, the others were Avensis. Did she know what model it was?’

Gillard shook his head. ‘I think she was doing well to recall as much as she did. Whatever model it was it had gone from its parking spot by the time the first uniform officer got there.’

‘Well, that gives us just a couple. One an Estima, one an Avensis. Of course with the snow melted, it’s hard to find much resemblance between the two vehicles.

‘Kirsty said the vehicle had only a little snow on it, which to me indicates it hadn’t been parked long.’

‘Sounds reasonable. The nearest ANPR or traffic camera is quite a way away, so none of it’s going to be easy to check.’ Hodges rewound the footage on the level crossing camera. ‘That’s the first Toyota we’ve got coming back. It’s got alloy wheels, like the one tailing Mrs Roy.’

Gillard peered at the screen. ‘Can you get any better resolution on this? I really can’t make out the driver. Just a dark shape.’

Hodges paused the video and zoomed in on the driver side window. The figure within was just a blur. ‘That’s the best we can do, I’m afraid. We can send it off for professional enhancement if you want?’

‘Yes, let’s do that.’

Hodges was also the evidence officer for this case, and Gillard wanted to take a fresh look at everything they’d got in case they had missed anything. Normally evidence in a current case as hot as this one would be kept on-site, but the sheer volume of the food, medicines and household items which had been tested for thallium meant that the majority of the bagged evidence was kept off site in a secure warehouse at the Guildford suburb of Burpham. After the short drive to get there, Gillard and Hodges used the card reader to gain access, and headed for the shelves dedicated to the contents of Mrs Roy’s two bathrooms.

‘Okay,’ said Hodges. ‘The top shelf is everything we took from the bathrooms and kitchen in Richmond. The shelf below is the stuff from her flat.’