‘Towards the end of our second year, Zoe and Christopher ended up at the Maths Society’s annual do. I wasn’t feeling well so I didn’t go. Everyone was drinking tons and some genius thought it would be a good idea to ply Christopher with vodka. Zoe said he got sick and she felt bad for him so she offered to escort him home. They had to pass by her rooms on the way to the place he stayed with his mum. He begged her to let him sit for a while in her room and sober up. He said his mum would kill him if he came home drunk. So she made them both some coffee and everything began to get really swimmy and odd. It could have been all the drink that night but Zoe could take her drink so I’ve always believed that Christopher slipped her something. She didn’t remember anything else, but I do.’

‘You were there?’

‘I was in bed in my room which was on the same floor, but I had to get up to pee and the bathroom was down the corridor. There was a light on in Zoe’s room. Not the main light, but, like a bedside lamp. I called her name and when she didn’t answer I tried the door. Christopher had obviously thought to put the chain on but it wasn’t locked so it swung open just enough for me to see Zoe lying unconscious with Christopher on top of her and—’ She stops. ‘I can’t tell you how many people I had to relate that story to afterwards. Police, the university security, the university authorities, Zoe’s parents, my parents, lawyers. It was like it became the only story ever told.’ She looks up at him and sees a pair of kind eyes looking back. ‘But I haven’t told it for a long, long time.’

‘Don’t go on if you can’t manage it.’

‘No, it’s OK, I want you to know. When I saw what was happening, I shouted to Zoe through the crack in the door, but she didn’t respond. I think I said something like, “Get off her,” and I saw Christopher freeze. I tried to curl my fingers around the door to slide the chain but I couldn’t reach it, so I took off. I was in a panic and I couldn’t think who to tell. It was late, there were no staff around. I ran around campus until I found a security guard at the gate. I had to explain what I’d seen to get him to agree to come. Eventually he did. By the time we got back and he let us in, Zoe was still on the bed, unconscious, only now she was alone.

‘The security guy just shrugged and said, “She’s out of it.”