Generous spirit behind visions of a bleak future

He began writing dystopian science fiction in the mid-Fifties with such wonderful novels as The Drowned World, The Burning World and The Crystal World, as well as many short stories, all dreaming of universal cataclysm, dispassionately presented, the characters simply accepting the deranged worlds in which they find themselves.

Many of these stories feel weirdly prescient now, as we face global warming and overpopulation. In Billennium, for example, published in 1961, overcrowding is such that the government allows a maximum living space per person of four square metres and the streets are so full that pedestrians become gridlocked for hours.

After the death of his wife in 1964, Ballard's harsh imagination took an even darker turn, perversely linking sexuality and violent death, in the stories of The Atrocity Exhibition (1970). At least nobody could accuse Ballard of not following his imaginative bent, wherever it took him.

In the prodigiously offensive short story, "Why I want to fuck Ronald Reagan", a supposed scientist offers clinical reports on subjects' violent fantasies in relation to Reagan, involving "Cadillac rear exhaust vents" and "Vietnamese child-atrocity victims".

Ballard upped the ante with his notorious 1973 novel Crash, presenting death and mutilation on the road as orgasmic, "millions of vehicles hurled together in a terminal congress of spurting loins and engine coolant". Although Ballard later changed his style, he never abjured his "deviant thesis", saying proudly "if The Atrocity Exhibition was a firework display in a charnel house, Crash was a thousand-bomber raid on reality".

At the time, Ballard's readers could have had little idea of the source of Ballard's peculiar imagination. That all changed when, in 1984, he published his marvellous, wholly realistic novel, Empire of the Sun, describing his three-year internment as a boy in 1943-45, thriving in a brutal and illogical world, during the Japanese occupation of Shanghai.

At once it was obvious that this was the experience that had shaped all his fiction. Why had he waited so long to tackle it directly? Ballard himself said it had taken him 20 years to forget Shanghai and then 20 years to remember it - and, interestingly, that he felt he had had to wait for his own children to become grown-ups first, being "too protective of them to expose them in my mind to the dangers I had known at their age".

Some of Ballard's fans, such as Martin Amis, actually felt betrayed by the disclosure - "the shaman had revealed the source of all his fever and magic".

But knowing the ultimate origin of Ballard's sense that the world can suddenly be turned upside down and that people are not naturally good doesn't lessen his visionary power. Many of his later novels, about such subjects as gated communities, high rise buildings, and urban collapse, remained ominously predictive.

Ballard had said that after his autobiographical novels - Empire of the Sun was followed by The Kindness of Women - he'd write no more about himself.

That changed when in June 2006 he was diagnosed with cancer. Last year, with thanks to his doctor, he published an admirable memoir, Miracles of Life, gently and gracefully revisiting his past for the last time.

Its decency seemed at odds with much of his fiction. But that was Ballard's paradox. This most violent, apocalyptic and perverse of our contemporary novelists was also a man most generous in spirit.