Sarah Durdy decided I was worth befriending at the beginning of sixth form because she wanted to go out with the boy whose best mate was my boyfriend at the time. She thought I could help her to achieve this, and I did. We remained friends after we’d dumped them. Sarah decided we needed to look further afield; the boys at our school were immature creeps, she said. We needed real men. Her solution was for us to join a tennis club.

I’d never been remotely interested in tennis or any sport, but it didn’t occur to me to say no. I looked up to Sarah. She got what she wanted in all things; it never crossed her mind that there might be any other outcome. I admired that. And one of the things she wanted was full ownership of me. It occasionally felt stifling, but mainly I liked it. Sarah acted as if I belonged to her; meanwhile, chez Tribbeck, I continued to feel more like a visiting foreign exchange student who had overstayed her welcome than a member of the family.

Within a couple of weeks of us joining the tennis club, I’d met someone I fancied in a frenzied, out-of-proportion way. He wasn’t a grown man but he wasn’t a boy from our school either. He went to a boarding school in Oxfordshire, and was only around in the school holidays, he told me. His name was Dorian, and he was so gorgeous that it didn’t matter. He could have been called Toenail and I’d have felt the same.

Sarah said she thought he was aloof and superior, but was encouraging nonetheless. She told me to go for it, ask him out, he might be less full of himself than he seemed; she’d never ask him out in a million years, but I definitely ought to.

So I did. And to my astonishment he said yes.

Sarah turned away when I told her the amazing news, as if I’d slapped her across the face. I was scared. I’d seen her freeze others out before, but she’d never been like that with me. ‘What’s wrong?’ I asked her.

‘Nothing,’ she said angrily. ‘It’s just, I would have thought you’d have noticed, that’s all. Seeing as how you’re supposed to be my best friend.’

‘Noticed what?’ I asked, utterly bewildered.

‘That I fancy Dorian too!’ she spat at me. Then she started to cry and said, ‘I’ve tried to keep it to myself because I could see how much you liked him. I did what a good friend does: I stood back, I supported you … And you didn’t even care that I liked him too! All you cared about was your ugly selfish self.’