She hands the binoculars back to Hart. ‘To the right of the steps,’ she says. ‘Far end of the beach.’

Hart adjusts the focus. ‘Ugly bastard, isn’t he?’

‘It’s definitely him,’ she says, watching as Strover pulls out the CCTV photo and passes it to her. Seeing the image again just makes her more sure. She misses this, the satisfaction of a match. It masks the fear. The professor who tested her said that super recognisers tend to peak in their mid-thirties. She should be in the zone.

‘Let’s have a little chat with him,’ Hart says to Strover. ‘Ask if he’s ever worked at the Bluebell.’

They return the binoculars to the Coastwatch volunteer in the lookout and set off along the path at the top of the cliffs, heading back towards the beach. Herman is still there, but he’s not settled and their pace quickens, Hart walking out ahead. It will take them a good ten minutes to reach him.

‘Can I ask you something?’ Kate says to Strover, who is beside her, one eye on the beach. ‘About facial-recognition software?’

‘Not exactly my favourite subject at the moment,’ Strover says.

‘Really?’ Kate’s surprised. Strover used to live and breathe technology when they worked together.

‘It keeps getting it wrong,’ she says.

‘I thought you were the tech expert?’

‘It’s all relative,’ Strover says, nodding at Hart ahead.

‘I heard that,’ Hart says.

‘I just want to know how easy it would be to find your double – you know, your lookalike.’

‘Aren’t there apps that can do that?’ Hart asks, chipping in. ‘“Find My Doppelgänger”.’

Hart’s not helping here. Kate’s trying to have a serious conversation with Strover, distract herself from Herman up ahead.

‘In theory, it should be easy,’ Strover says. ‘As you know, the software relies on metrics – the distance between eyes, ears – and data. The more of it, the better. Apps only have access to a limited number of photos. But law-enforcement agencies can draw on millions of images – the UK custody database is getting bigger every day.’

‘And in reality…?’ Kate asks.

‘You might get a rough match, but finding your long-lost twin is by no means a given. Someone who looks identical might not share the exact same facial geometry.’

‘It’s why we turned to people like you,’ Hart says. ‘Faces are uniquely human. They need to be interpreted emotionally, intuitively, not just measured. At least that’s what I told the boss.’

‘Can I ask you a favour?’ Kate says. ‘In return for helping you guys out with the photo.’

‘Depends what it is,’ Hart says.

‘I want you to look for a match for Rob. My partner.’

‘Isn’t that a bit weird?’ Hart says.

Strover gives him a look.