The thought hit me with such extraordinary power that my legs almost gave way beneath me. I walked a few steps to one of the benches that surround the duck pond on the edge of Barnet, and sat down. My heart was racing, my breathing shallow, I was covered in a sweat, and I thought for a moment that I might pass out or throw up. After a decent while I decided I would do neither. And I got up and went to the supermarket, for my wife was in hospital and was filled with a passion for fresh fruit.

What if he has Down’s syndrome? That was the sudden question that had overwhelmed me. My first child was to be born any day and there were complications, which was why my wife was in hospital. So naturally I was full of nerves, as a first-time parent must be. The duck-pond incident was an attack of the horrors: I imagined a situation so terrible that it almost robbed me of consciousness. Down’s syndrome! The horror, the horror!

Well, he didn’t. Joseph was born the next day by Caesarean section, and has no problems beyond his own singularity of nature. Joe is great: Cindy and I were, if you’ll forgive the word, blessed, and life carried on in a new and extraordinary way. So far, so ordinary.

Seven years later we had another child. He does have Down’s syndrome. We had been told after the second scan that there was a 50 per cent chance of this. I accepted it as a 100 per cent certainty. Or was there just a tiny, 1-per-cent pinhole of hope? Hope against hope? But no, I told myself, resign yourself. And I remember clearly another of those moments of pre-birth terror. I’m sure we’ll deal with it, I thought, whatever happens.

And they’ll say, Simon, well, bloody hell, you know, he’s a saint, the way he looks after that boy. And I thought: I don’t want to be a bloody saint. I want to enjoy my life, not dedicate it. I have no ambitions at all when it comes to sainthood.

And do you know what? I haven’t become a saint. It’s a complete triumph: I have found no need for canonisation whatsoever. Nor did I have to work hard at resisting sainthood. Unsaintliness came quite naturally. Eddie — Edmund John Francis — was born on May 23, 2001. He has Down’s syndrome all right.

He has me as his father, and his father is not a saint. His father also enjoys his life very much, and Eddie does not compromise that: au contraire.

Eddie enjoys his life very much too, most of the time: he makes that quite clear. And when he doesn’t, he makes that pretty clear as well. Being a child.

The human imagination can do many extraordinary things. But we can’t imagine love. Or perhaps I mean loving: love as a continuous state; one that carries on in much the same way from day to day, changing and growing with time just as people do. The great stories of literature are about meeting and falling in love, about infidelity, about passion. They are seldom about the routines of married life and having children.

We can imagine dramas and turmoil. People make films about them. In our own minds, we often put together the most terrific stories about thrilling or devastating events that might befall us. But what no one can imagine is the day-to-day process of living with things and getting on with the humdrum job of loving. We can imagine only the beautiful and the terrible. We are drama queens, and our imaginations are incapable of giving us any help about coping from day to day. Marriage is not the same as falling in love; nor is it an endless succession of terrible rows and monumental reconciliations: it is about a million small things: things beyond our imagining.

By the way, I hope you are not too squeamish. This piece is not going to pull any punches. If you find the idea of love uncomfortable or sentimental or best-not-talked-about or existing only in the midst of a passionate love affair, then you will find problems with what I am writing. I am writing of love not as a matter of grand passions, or as high-falutin’ idealism, or as religion. I am writing about love as the stuff that makes the processes of human life happen: the love that moves the sun and other stars, which is also the love that makes the toast and other snacks. Love is the most humdrum thing in life, the only thing that matters, the thing that is forever beyond the reach of human imagination.

So no, I couldn’t imagine what it was like to live with a child who had Down’s syndrome. I could imagine only the dramatic bits: the difficulties, the people in public places turning away in shock and distaste, the awfulness of a child who couldn’t say his own name.