At first I - I felt that it was confined to my liver and that they had - the operation had completely removed it. And so I felt quite relieved. And then that same afternoon we had an MRI of my head and neck and it showed up that it was already in four places in my brain. So I would say that night and the next day, until I came back up to Emory, I just thought I had a few weeks left. But I was surprisingly at ease. You know, I've had a wonderful life. I've had thousands of friends and I've had an exciting and adventurous and gratifying existence. So I was surprisingly at ease, much more so than my wife was.

I cannot pretend I am without fear. But my predominant feeling is one of gratitude. I have loved and been loved; I have been given much and I have given something in return; I have read and traveled and thought and written. I have had an intercourse with the world, the special intercourse of writers and readers. Above all, I have been a sentient being, a thinking animal, on this beautiful planet, and that in itself has been an enormous privilege and adventure.

I’ve had a couple of ex-girlfriends sort of accuse me of having a personality disorder! … No, I don’t know. I’ve always been afraid of death. I’ve never wanted to die. Last year, I watched this guy die in Red Rock. It was this horrible freak accident thing. He fell and he cracked his head and basically just bled out. That was the first time I’d ever actually seen a climbing accident like that. It was kind of sobering — he was even wearing a helmet — it was a reminder of how dangerous climbing can be if things go wrong even when you have all the ropes on.

I've always felt that death is the greatest invention of life. I'm sure that life evolved without death at first and found that without death, life didn't work very well because it didn't make room for the young. It didn't know how the world was fifty years ago. It didn't know how the world was twenty years ago. It saw it as it is today, without any preconceptions, and dreamed how it could be based on that. We're not satisfied based on the accomplishment of the last thirty years. We're dissatisfied because the current state didn't live up to their ideals. Without death there would be very little progress.

When my father was in his terminal year, I discussed death with him. I recall very clearly his relief that the cancer that was taking him was at least allowing him "all his marbles". Dementia in its varied forms is not like cancer. Dad saw the cancer in his pancreas as an invader. But Alzheimer's is me, unwinding, losing trust in myself, a butt of my own jokes and on bad days capable of playing hunt the slipper by myself and losing. You can't battle it, you can't be a plucky "survivor". It steals you from yourself. And I'm 60; that's supposed to be the new 40.

It occurred to me that at one point it was like I had two diseases – one was Alzheimer's and the other was knowing I had Alzheimer's. There were times when I thought I'd have been much happier not knowing, just accepting that I'd lost brain cells and one day they'd probably grow back or whatever. It is better to know, though, and better for it to be known, because it has got people talking, which I rather think was what I had in mind.

When Milton's Satan stood in the pit of hell and raged at heaven, he was merely a trifle miffed compared to how I felt on that day. I felt totally alone, with the world receding away from me in every direction, and you could have used my anger to weld steel. Only my family and the fact I had fans in the medical profession, who were able to give me useful advice, got me through that moment.

I remember what George said and vowed that rather than let Alzheimer's take me, I would take it. I would live my life as ever to the full and die, before the disease mounted its last attack, in my own home, in a chair on the lawn, with a brandy in my hand to wash down whatever modern version of the "Brompton cocktail" some helpful medic could supply. And with Thomas Tallis on my iPod, I would shake hands with Death.

Let us consider me as a test case. As I have said, I would like to die peacefully with Thomas Tallis on my iPod before the disease takes me over and I hope that will not be for quite some time to come, because if I knew that I could die at any time I wanted, then suddenly every day would be as precious as a million pounds. If I knew that I could die, I would live. My life, my death, my choice.