‘What time did the train arrive at Clapham Junction?’

‘It was on time, arriving at 16.40.’

‘So just one minute after the last text was sent, saying she was just arriving.’ Gillard looked around the table. ‘The thing that baffles me is that we have two completely different narratives for Beatrice Ulbricht’s movements. We have the one we can see, where she travels for forty-odd minutes on the train and then, poof, disappears. Then we have the electronic story, which has an utterly consistent cell site record seemingly for the entire trip. That includes two texts definitely sent from the train, and then an autonomous trip in a rubbish container to Brentford.’

They all sat for a minute pondering this conundrum.

Claire spoke up. ‘Is it conceivable she could have been murdered on the train and someone else took over her phone?’

‘There were lots of people around,’ Gillard said.

Duffy nodded. ‘There is almost no chance. This isn’t like the old days with slam door carriages, when you could conceivably throw a body off the train. On some of the older intercity coaches with droplight windows, where you reach out to externally open the door, you could still do it. But modern commuter train doors will not open while the train is moving.’

‘What about the interconnecting corridors between carriages?’ Townsend asked.

Duffy shook his head. ‘The concertina sections are bordered by glass doors, so someone would have seen. There are no gaps to get a body onto the track. Besides which, if she was on the track we would have found her by now. As I mentioned in my email, the entire train was searched as soon as we were notified, though it would have undertaken six or seven further journeys in that time. Nonetheless, we also stripped the cover from the seat she was identified to have been sitting at, and have supplied that to you in case you want to do any forensic analysis.’

Gillard picked up the DI’s defensive tone. ‘Thank you for that, Nigel. We appreciate what you and everybody at BTP have done. Of course, we still haven’t finished going through the miles of CCTV footage on each and every platform for the ten stations between Clandon and Clapham Junction. That might provide us with some answers.’

‘Logically, there is only one possibility,’ Rob said, counting off on his fingers. ‘If the phone says she was on the train approaching Clapham Junction, and if the cameras showed she never got off after Clapham Junction, and Nigel here says she couldn’t have been murdered on the train, then—’

‘She stayed on at Waterloo and waited to be whisked back towards Guildford!’ Claire said.

‘Exactly, but dumped the phone in the bin,’ Townsend added.

‘If she stayed on, there will surely be witnesses,’ Gillard said.

‘Why on earth would she stay on?’ Duffy asked.

Gillard shrugged. ‘No idea, maybe she forgot something. We’ll deal with that later. But if she did, then there is a good chance she is still alive, somewhere.’