She still doesn’t understand exactly what Rob does in London. One of the articles she read about his meteoric career described him as a serial ‘techpreneur’, the youngest ever founder of a British ‘unicorn’ company and a pioneering champion of something called ‘direct neural interface’ technology – the interaction between brain and machine. She likes the sound of unicorns. The ‘disruptive’ tag is less appealing. He also runs a charity on the side that puts on art shows in hospitals, which is how they met.

‘That’s so interesting,’ she offers, filling the silence. ‘You’ve developed an app, you say, that makes women wake up in the middle of the night begging to give their man a blowjob? That’s incredible. What a smart, selfless piece of coding.’

He nudges her playfully. And then all she can hear is the faint in and out of his breathing, and the sound of the waves below.

Sleep soon starts to lap at her own consciousness, but something’s preventing her from dropping off. What Rob said about doubles last weekend has been on her mind all week. She hasn’t been able to forget it, his words chasing her through her days of painting and nights of restless dreams. And I’ve already met mine, a long time ago. What must it be like to actually meet your double? And when did Rob encounter his? Where? We’ve all got a double out there somewhere, watching, waiting. Shadowless. It’s revealed an unexpected side of him. A new insight.

She turns over, her interest piqued all over again. She remembers being fascinated by identical twins in primary school. The teacher used to tell her off for staring at them in class. Maybe it was an early challenge to her powers of recognition. Spot the difference. And there was the French-exchange girl at secondary school who apparently looked just like her. That had freaked her out.

She lies there, sleepless, her thoughts running loose and wild. What if the French girl were to suddenly come back into her life, discover her on Instagram, decide she’d like a piece of Rob… What was it he said? It’s well within the bounds of probability for all of us to be found by someone with an exact physical likeness. Would Rob be attracted to her? The woman would have a fight on her hands if she tried it on with him. Kate smiles at the ceiling. It’s a preposterous thought. But then she recalls Rob’s tone of voice, how serious he’d been, and her stomach tightens. He’ll take over my life, me, you, the house, my company, all that I’ve achieved, everything’s that’s precious to me. Imagine living with that sort of fear. And what if it became reality? She shoves the idea to the back of mind.