Then again, perhaps he isn’t. He could have been married to her later on, after 1976. But it’s certainly possible that he is the person Anna had a child with back then. And that child could well be me.

It’s probably only a two-minute walk but it takes me a dozen. I sit on a bench by the church – a beautiful white chapel with a tall spire covered in slate tiles – and stare at a field where brown horned cows are grazing, heavy bells around their necks. Part of me wants to head right back to the train station and get as far away as possible, take a plane from Geneva and go back to the UK to see Dad and Maggie and forget I was ever here. But another part is drawing me towards Daniel Buchs’ house, where perhaps, finally, I’ll understand something of who I am.

I take my phone out of my bag and read the last text message I got from Dad.

Nice evening with Bob and Ken in the pub. I won the pool. Going to London to see Maggie’s show tomorrow. I’ll report back. Love Dad x

Nothing could replace the years of Dad being Dad. Nothing could change the memories we share, the interests we have in common, the way we see eye to eye on politics but rarely like the same movies. Our shared eye-rolling at Aunt Jemima’s latest hare-brained project. The way I always tease him about his outdated dress sense and his penchant for kippers. But would something change if I met my biological father?

What, I’m not sure, but it feels like Pandora’s box and I don’t know if I want to take the risk of opening it, just as I couldn’t bear the memory of Mum to be in any way altered by meeting Anna.

It’s not like I have anyone else to ask because it’s not as if there are many of us. I know, having spent a considerable amount of time searching online, that there are other, similarly bizarre cases: twin boys adopted at birth who grew up in different families, neither knowing about the existence of the other; a British girl who only found out at thirty that she had been adopted as a baby, and then traced her birth mother to Argentina. Maybe they would understand. But what am I meant to do? Call them up? It’s hardly feasible, and even if I could, the idea makes me feel slightly sick.

It’s like being part of a strange club that no one actually wants to be in. The ‘What If?’ Club. The Alternative Lives Club. I don’t want that membership card.