But if I was sitting in an armchair with bits and pieces of rubber sticking out of me and my son came over and said, you know, would you like a banana? Wink once for yes, wink twice for no, I dont think the interest of the conversation would get me past the sense that this is horrible. It's horrible for me but above all, horrible for them. There are things worse than death.

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 don’t think so! You can’t really know that until the moment of your death, at which point you will probably not be afraid because you won’t be there. I have a very old friend who called me last year to say, “Okay I am done. I am not fighting this anymore. I am checking out. I am calling to say goodbye because I am not really conscious most of the time. I am cutting off the pain killers.” He seemed okay. That was not the moment of his death, but it was within two or three days.

The chief side effect of this pain is numbness in the extremities, filling me with the not irrational fear that I shall lose the ability to write. Without that ability, I feel sure in advance, my “will to live” would be hugely attenuated. I often grandly say that writing is not just my living and my livelihood but my very life, and it’s true. Almost like the threatened loss of my voice, which is currently being alleviated by some temporary injections into my vocal folds, I feel my personality and identity dissolving as I contemplate dead hands and the loss of the transmission belts that connect me to writing and thinking.

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 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.

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.

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.