‘I only brought the one with me,’ he said, showing them the slightly newer one from 1746. It was a lie; the other was still in his pocket, but some mistrustful instinct made him keep it hidden. The detectives examined it with impassive faces, then Macleod asked if they could hang onto it as evidence. Ewan, who had seen this coming, reluctantly agreed. Coull put the coin in a little plastic bag and assured him it would be well looked after.

‘Don’t forget to drop the other one into the station when you get a chance,’ said Coull.

‘Of course,’ replied Ewan, thinking he’d do no such thing.

‘Now tell us again about this poacher who claims to have witnessed the alleged incident,’ Macleod said, leaning across the table with his chunky square hands laced in front of him. The term ‘alleged incident’ grated on Ewan somewhat, but he patiently and politely repeated what he’d already told them.

‘Like I said, that’s all I know about the man. I don’t know his name, or exactly who or what he saw, other than he witnessed four men pushing Ross into the loch and deliberately drowning him. He couldn’t swim, anyway.’

‘Couldnae swim, eh?’ Coull asked, glancing sideways at his colleague as though this were some suspicious detail critical to cracking the case. By now Ewan was starting to get peeved by their lacklustre response. He asked them what they intended to do about this, now they had the facts of the matter before them.

Macleod heaved his thick shoulders in a shrug. ‘To be honest, Mr McCulloch, I would hardly say we had the facts. What you’re reporting is essentially no more than hearsay. These are very serious allegations and require more than this kind of flimsy anecdotal evidence to support them.’

‘Well, if you wanted something more substantial to go on, you could try to identify the witness, for a start,’ Ewan said.

‘Alleged witness,’ Coull corrected him.

‘Okay, alleged witness,’ Ewan said with a flush of impatience.

‘And how do you propose we do that, Mr McCulloch?’

‘Given that he seems to be in the habit of poaching salmon on the loch, he might not be that hard to find. He told me he’d been caught before. So maybe he’s already on file somewhere. I mean, you must have a database of all the people who’ve been prosecuted for that sort of thing.’

‘You’d have to narrow it down to something a wee bit more specific,’ Coull said. ‘We don’t know when he was caught, or doing what exactly, or where. That’s an awfy lot of potential names to trawl through, each one of which would have to be processed individually. You’re talking an enormous expenditure of manpower.’