Sara sighed. ‘Difficult to say. I need to speak to the tech guys and see if there’s a way it could’ve been done remotely. Leave it with me.’

Caroline thanked Sara, feeling once again as if they’d hit a brick wall. Every time there was the possibility of a lead or a breakthrough, it seemed as though something else pulled the rug from under their feet.

Barely a few seconds after Sara left, there was a knock at the door.

‘Come in.’

‘Got something for you,’ Aidan said. ‘Phone records for Patrick Walsh. Could potentially be good news, but there’s a caveat.’

‘Go on.’

‘Okay. On the night Roger Clifton was murdered, Walsh definitely wasn’t at home. Based on cell site data, if he had his phone on him, he wasn’t even in Oakham. But coverage is patchy, so we can’t pin him down exactly. There’s actually a pretty wide area he could’ve been in — nearly ten kilometres across — but guess what’s right near the centre of it?’

‘Please tell me the answer is Normanton Church.’

Aidan passed her a sheet of A4 paper, on which a map was printed, showing the overlay of the cell site data. Every mobile phone constantly pings nearby cell towers to maintain a reception, and most are connected to multiple towers at once. Each tower doesn’t know where that mobile phone is, but it does know its distance. By knowing a phone was a specific distance from multiple different masts, it was possible to narrow its location down to within a few feet in some areas of the country. In Rutland, however, where cell masts were few and far between, it was a very different matter.

‘Jesus Christ. That’s amazing, Aidan,’ Caroline said, confirming her hopes that Normanton Church sat nicely in the middle of the area in which Patrick Walsh’s phone was known to have been.

‘It is, but it’s nowhere near enough. There are a million and one other places inside that patch where he could’ve been. It still doesn’t place him at Normanton.’

‘It doesn’t, but it’s a bloody good start. It’s another step closer, without a doubt.’

‘Certainly doesn’t take him out of the picture just yet.’

‘It’s more than that. This might even be enough to bring him in and start to pick holes in his story.’

‘Perhaps. I’m not so sure. I think we need something more concrete before we bring him in. We don’t want him wriggling off. And if it’s not him, we’re up shit creek without a paddle. The guy’s virtually a celebrity.’