I've been wanting to write for so many years to express my gratitude and my sorrow. The anniversary was a few weeks ago. A terrible anniversary for you, but marking the day I started to live again. It was "a good kidney", they said; but what they meant was that a young, healthy man had died.

I was 15 years old and I was dying, after more than two years on dialysis and some major complications. Being on dialysis is not a good way to live now, but back then it was worse, particularly for children. Mercifully, I was young and my mind was dulled, and it never occurred to me I might die; but it must have been obvious to everyone else.

I hadn't been to school for a year, and every other day I spent an uncomfortable four hours on the dialysis machine. My raw teenage emotions found something to cling to in the form of the good-looking young doctors and kindly nurses, but even my feelings were becoming distant and quiet. I suppose all systems were closing down to concentrate on surviving.

My mother woke me in the middle of the night to say there might be a kidney for me, and we made the very familiar drive to the hospital through a snow storm. Was it the snow that killed your relative? A car crash? I don't know.

When I woke from the anaesthetic, I felt different. There was a new energy in my body, as if I could run for miles. Of course I couldn't - it took at least a year to get back to full health. But something had changed, immediately.

Of course, no one lives in a haze of gratitude and awareness for two decades. Sometimes I feel it as a weighty duty in which I am failing: as if, having been given that rare and precious second chance, I should use my life wisely, when actually it has often been a struggle for meaning and peace.

But I do not have to struggle for my health. Most people don't know I've had a transplant; they just see a healthy, fit and active person. Without the kidney I would not have grown up, gone to university, travelled round the world, fallen in love or known my nieces and nephews.

This kidney cleans out the toxins that would otherwise kill me, but it is more than a sophisticated pump. It's a piece of someone else. I think of it as a sort of physical memory - while I live, your relative is not quite gone. You will have real and precious memories but while I know nothing of your relative, he is in my thoughts a great deal. So are those who loved him.

"Thank you" do not seem adequate words, but they're the best we have. So thank you very much for your act of generosity all those years ago, from which I am still benefiting so hugely. Thank you from my parents and my brothers, who were also able to live a normal life again, without anguish and dread. Thank you.

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