‘What? Like thinking Wednesday is blue and six? Monday is yellow and three? That kind of thing?’

‘No, not like that.’ She frowned and wrapped her arms round herself. ‘Not like that.’

‘Like what, then?’

‘What you’re talking about is to do with language and experience. You’re responding to words, labels, and your experiences of them. Everyone has colours they prefer, numbers they like — maybe because of their shape or something.’ She reached for her glass of wine as lightning razzled across the bay, making cliffs and beach jump purple. ‘I mean like that -the sky changes and I taste sour lemon. I see the flash and I taste lemon.’ She looked away from me, out to sea. ‘When it’s really bad I don’t even see the lightning, I just taste lemon.’

‘Jesus Christ.’

She wakes to the alarm on Monday mornings tasting peaches, she listens to opera and sees John Martin’s vast canvases. She eats spaghetti and her hands tingle as if a bolt of silk is being pulled through them. Eating in a restaurant is always an interesting experience.

‘How was your fish, madam?’

‘Wonderful, like aluminium.’

Sometimes it’s worse than other times. Sometimes she can’t function very well because her vision, her interpretation, of the world is so at odds with the rest of ours. Most of the time it’s not so bad. She says that she would rather be a synaesthete than colour blind. But, then, she was always an optimistic synaesthete — as I realised when she described my touch as being burgundy wine. And now I understand what she means: my touch is not like burgundy wine, it is burgundy wine.

I remember looking out at the volcanic arch and thinking, Well, that’s just fine.

Twenty years is a long time; it used to be a generation. Sonja and I have lived half our lives together. And all around us people have failed at the one thing they wished to do well — to love someone and to stay with them. So simple. So why is it that over the years friends have come to us in pieces, fragmented wrecks, and cried in front of us, as Sonja makes pictures of their words and I watch their faces and their mouths work? We have always been the constant, the given, the exemplar.

Sonja and I don’t have children. I’m not sure when we made that decision; I’m not even sure if it was a decision, a choice. I don’t know. I woke up one day and realised we were both forty and childless, realised that all we had was each other. Which was enough for me because if children had arrived they would have brought change and disturbance with them. Our lives would have been bent out of shape, twisted by unfamiliar uncertainties and unexpected fears. Besides, I’ve never been quite sure what fatherhood means.

I am a carpenter. I shape wood so that it will fit together one way or another, and I sometimes think my mother’s disappointed that this is what I do. I left King’s College after a year and trained for a City and Guilds diploma. One Friday afternoon I climbed on my motorbike and drove to Sonja’s halls of residence, swerving and listing violently at high speed, because I wanted to get to Sonja. (I have always wanted to get to Sonja.) I burst into her room, wearing sawdust-covered dungarees and a motorcycle helmet and asked her to marry me and she said she would. Her friends exclaimed, talked of the romance of what I had done. I didn’t have the heart to tell them it wasn’t romance; it was loneliness that prompted me.