END OF STORY

I saw Martin down the caff on Monday. I used to be Martin's nurse, and after I left the hospital we kept up. Martin is a chronic schizophrenic, who, if he misses his monthly injection, is afflicted by the spectacular delusion that London has been devastated by a nuclear holocaust.

Unusually, the onset of Martin's illness can be accurately pinpointed to a particular autumn afternoon about15 years ago when he picked and ate more than 500 magic mushrooms. "We picked them by torchlight," he told me. "I'd never seen so many in one field. After the first 50 or so I could hear individual mushrooms calling out to me."

If you ask him to, Martin does a little high-pitched imitation of what a magic mushroom sounds like. "Martin! Martin! Over here, Martin!" he trills, without embarrassment. When he describes his holocaust delusion, he is describing Berlin immediately after the Second World War, with its ruined buildings still standing and great mountains of rubble, rather than Hiroshima or Nagasaki where everything is totally flattened. As well as his nuclear holocaust delusion, since eating the mushrooms Martin's mind has been inhabited by two personalities, Mungo and Sophie, who constantly bicker about him, but it is the nuclear thing I want to tell you about.

In recent years, Martin's life on the outside has been governed by another spectacular delusion - an officially recognised one this time - known as "care in the community". He has been given a bed-sit on a refuse tip of a housing estate, and his health care consists of occasional visits from a community psychiatric nurse, and if Martin has run out of Old Holborn he might look in at the day-centre. For a person suffering from periodic bouts of psychosis, it couldn't be a worse situation. For one thing there is always a little band of novice drug-users in Martin's bed-sit, teenagers mostly, who are either skinning up, or jacking up, or sitting motionless. These teenagers look up to Martin for having taken the audacious step of losing his mind, and he presides benignly over them like some sort of Grand High Satsuma of the Temple of the Inner Splendidness.

It isn't just the drugs being passed around that are working against Martin's chances of recovery. Every kind of occult practice imaginable is carried on in and around Martin's flats, from voodoo to the bizarre vilenesses rumoured to have been perpetrated by a Satanist church which meets on the 12th floor. The entire council estate seems to be inhabited by dreamers, babblers, visionaries and savants. As I say, hardly the ideal environment for a recovering psychotic.

I hadn't seen Martin for a while when I met him in the caff. Over tea and scrambled eggs he told me about this strange and evil book currently being passed round the estate. Nobody knows where it came from, but, once opened, it exerts a strange power over the reader, to the extent that readers become so drawn in by the story they actually believe they are living in it. As the book has passed from hand to hand, dramatic nervous breakdowns have occurred in its wake. "Martin Amis's latest?" I asked. "I don't think so," said Martin, who was either unfamiliar with Martin Amis's oeuvre, or remaining remarkably opened-minded about the whole affair.

The reason I hadn't seen him about lately, he said, was that he has been feeling strangely oppressed, as though some terrible catastrophe was about to happen. This feeling had so overwhelmed him that he couldn't function properly, and he had drawn the curtains, got into bed and stayed there for two weeks. He must have been bad, he said, because he stayed there even after he had run out of tobacco.

"Were you paranoid?" I asked, all nursey-like.

"Paranoid!" said Martin. "I was bleedin' quadraphonic!"

"What did you think was going to happen?"

"I don't know. Everything felt sort of evil."

"And do you believe in the power of evil?"

"Nah. Not really."

Anyway, the long and the short of it is that, while Martin was in bed with the curtains drawn, council contractors came along and demolished three blocks of flats not far from his window.

So when Martin finally looked out, like Noah after the flood, the first thing he saw was the demolished flats. At which he automatically assumed that the old nuclear-catastrophe delusion was upon him, and he went back to bed.