‘But he was near to me, maybe fifty or sixty metres away.’

‘Witnessed by you and no one else,’ Naylor said quietly.

‘So what are you saying, that I sent those messages from Ben’s mobile? Why would I do that?’

Larssen put a hand on my arm.

‘Joe, take it easy.’ He turned to the detectives. ‘There was a Facebook post on Saturday evening. Mr Delaney said he was fine, and that he’d been away to think about things.’

Naylor flipped to another page in his black ring binder.

‘OK. The Facebook post next.’

Something in the way he said it made the knot of fear in my guts grow heavier, but I said nothing.

‘Facebook always take bloody ages to turn over location data, so we don’t have much on that front yet. What we do have is a quick and dirty forensic authorship analysis, done by our friends at Goldsmiths College, of the Facebook post and those text messages. They can do an initial analysis in a matter of hours, and they’re always eager to help.’

He snapped the ring binder open and removed two sheets, laying them side by side on the table in front of me. The page on the right was a screengrab of Ben’s message from Saturday:

Needed to get my head sorted; it’s been good to get away. And I’ve always loved it when everything starts falling into place.

‘The truth of the battle is whatever the victor deems it to be . . .’

The page on the left contained multiple screengrabs of previous Facebook status updates. About work, football, cars, the economy, Apple, Google, new films and so on.

‘These are all Ben’s as well, are they?’

Naylor nodded.

‘They’re all from his account. So our pointy-headed friends at Goldsmiths do two things: the first is they run all the text through a piece of clever software they’ve written for the purpose. Then the linguistics bods do something called a subjective comparative analysis of different messages, comparing a set of messages with each other. That sometimes throws up areas of contrast that we might want to look at further.’

‘These all look like pretty bog-standard Facebook updates to me. Why is this relevant to him posting on Saturday that he’s fine?’

‘All right, here’s an example. How many times do you think Mr Delaney used a semi-colon in a Facebook post in the last three months?’

I’d been expecting something else and was momentarily thrown by the question. Ben was a computer guy, a techie, one of those blokes who viewed traditional grammar and punctuation on a par with quill pens and parchment. Which was to say: utterly redundant in the digital twenty-first century.

‘Seriously?’

‘Yes. How many do you think?’

‘Not many, I suppose. Never paid much attention to the stuff he puts on Facebook.’

‘Have a guess.’