‘Marianne loved this,’ he says, turning it over in his hands. ‘She was only twelve and we’d gone on holiday to Zakynthos in Greece and she’d been so excited about diving in the sea that she’d talked of nothing else for weeks before we even got on the plane. We’d got her goggles, flippers and a snorkel, and the minute we arrived at the hotel she was itching to get in the water. Of course, she’d been imagining this rich underwater world for so long that the reality was a huge disappointment. There were no bright coloured fish, or beautiful shells. It was mostly sand and the odd bit of rubbish which had got stuck on the seabed. She was so upset that I found a tourist shop and bought this, and the next morning I went down to the beach before breakfast and hid it by some rocks so I could find it later. She was pretty reluctant to go into the water again, but I persuaded her and made sure we swam near the rocks. She saw it of course and dived for it. At first she seemed really happy, but by the next day she’d lost all interest in diving and didn’t go in the water again for the rest of the week. As we were leaving the hotel I was checking her room and saw she’d left it on the bed. I packed it, and when we got back here I showed it to her, saying she’d almost left it behind. I’ll never forget the look she gave me. “It’s not real, though, is it?” “Of course it’s real,” I told her. “You put it there, didn’t you?” she said. I said no. She got her phone out, typed something in and showed me a Wikipedia page on this type of shell, which it turns out is slightly different from any found in the Mediterranean.’

He holds it up for us to see, turning it slowly in his hands. There’s a shiny curled inner lip and a spiky outside.

‘Lobatus gigas it’s called, and it’s only found in the northwest Atlantic. I lied to her, and she knew I was lying. The same way I’d held her whilst she was growing up and told her everything would be okay, reassured her that life was wonderful and that she was going to do great things. And all I can think about is that whilst she was … was being killed she must have known I’d lied again. Do you know what that’s like, to lie to your own child?’

He’s still staring at the shell when I prompt him on my original question, why none of the compounds the company was studying worked.