IN FROM THE COLD

Has Iain Sinclair, `alternative' writer-poet and chronicler of a dark and mystic London, joined the mainstream with his new book? Andy Beckett met him at home in Hackney

About this time last year, Iain Sinclair wrote a most strange and fearsome article. Asked by the London Review of Books to consider a weight of volumes about William Blake, Sinclair handed in his essay at twice the journal's normal length. He began stealthily, circling round the notion of biography, then started closing in on a single title, ignoring the other six books. The focus was Blake by Peter Ackroyd, alchemist of London's past, and Sinclair had a rather unorthodox idea about how to review it: "I broke the spine," he wrote, "and hacked the wad of text into portable portions, sealing each one in a plastic envelope - before setting off, on foot, to seek out the traces of Blake in the city."

Sinclair walked, a bald hulk of a man, reading and looking, following his own method for turning the capital into books. As he lingered in graveyards and strode through dimming streets, his own search for Blake came to overlay Ackroyd's. Sinclair mused out loud: perhaps he, not Ackroyd, was "the supreme Londoner", his better-selling rival "no more than a freakishly gifted mechanic". He decided that "Ackroyd was surely out there, mapping future fictions"; he would find and confront him, challenge his street knowledge. After tens of miles and thousands of words, in the heart of the City, Sinclair found his prey. The LRB letters pages were busy the following fortnight.

Iain Sinclair's reviews often glower. He recently dismissed Martin Amis as "a part-time anthropologist", and the year's young novelists as "women who photograph well". Sinclair recommends instead "that which seems most remote, alienated, fractured" - poets of chaotic syntax, occult cartoonists, near-forgotten chroniclers of London lowlife like Alexander Baron and Emanuel Litvinoff. His own novels, meanwhile, out-stare them all. Read aloud, with his gangster's rasp, at abandoned churches and nightclub happenings and the more arcane kind of bookshop, they flood a room with their violent density of effect and image, taking on Thomas Pynchon adjective for adjective in Camden Town. On the page, their ambition is still grander: to take the Thames and Limehouse, Jack the Ripper and Hawksmoor, all the city's power and conspiracies and squalor, and spread them out in a panorama worthy of Dickens and Conrad.

Since 1987, Sinclair has published four searches for this grail. His new book, Lights Out for the Territory, is more approachable, a fat work of non-fiction following him on actual walks across London, street by street, divining for secrets and meaning in the great grey labyrinth. Sinclair stalks Ronnie Kray's funeral swagger through Bethnal Green, shares the views from Jeffrey Archer's Vauxhall penthouse, spies in horror and awe on the pitbulls of Victoria Park. Through polemic and travelogue and memoir, the cruel and seething modern city emerges.

But Sinclair is still really writing the same book. His narratives are always quests; his sentences are fantastically barnacled with detail, mostly malign ("puce roses sweating with shame" on the Kray cortege), but sometimes lovely (a square "frisky with the dance of leaf-light"); his London knowledge oceanic, noting the "pigeon man" of Dalston on the same page as the area's market-garden past; and each drifting, verb-thin page takes several minutes to read.

The difference this time is that more people are trying. Sinclair is 53, with an age of self-publishing and small press printing and being discounted as "difficult" behind him. His fans have been fanatics, tracing occult paths of their own with his books on their handlebars. Now, he is published by the newly launched Granta Books, alongside Nigel Williams, the television-adapted comedian of a sunnier suburban London. He is taken out to lunch and asked to write librettos. Suicide Bridge, an obscure work from the seventies, has been reprinted for the coffee table. Cambridge students are writing PhDs on Downriver and Radon Daughters. Critics of last year's Booker Prize nominations cited him, as if by some strategy, as an exemplar of an alternative, bolder fiction. And all the while, Sinclair stamps his East End pavements, meets his mysterious collaborators, lets his reputation loom ever larger.

HE LIVES in Hackney beneath tower-blocks. All day the sky has been the colour of gravestones; by evening, it has lowered to a dead fog, thickened by the swirls of exhaust along the Queensbridge Road. On Sinclair's street, windscreen glass marks each parking space like confetti. That, however, is as grim as it gets. Albion Drive - aptly named for Sinclair - is peeling but elegant: a sliver of grey-brown terraces, white trim and pediments, leading the eye to a wide square beyond. There are discreet jeeps, plantings of bamboo: gentrification, Hackney-style.

Sinclair is wearing cords and slippers. He pads upstairs past stripped- down doors and yellow walls and settles himself, polished wood and cane to each side, on a sofa that might have come from Liberty. His wife brings a tray of tea and lemon.

Sinclair gets up to pour himself a whisky, and his chest is a barrel beneath his denim shirt, but his voice is quiet and mild. He small-talks, recommending kindred spirits, with the polite warmth of a good vicar. His wife teaches locally; her school is "pretty horrific". He describes his neighbourhood. When he moved in, in 1968, Albion Drive was cheap condemned land, in the path of the towerblocks. Except the money ran out - a ghost of a smile slips across Sinclair's big baggy face - and the Victorian enclave was spared. The council blocks decayed: "There were always jumpers from those flats," he says drily. "The next one's going to be blown up in January." Slowly, the area grew respectable: "The corner house on the square belonged to Charlie Kray when we moved in - then he went to prison." A few professionals arrived, drawn by the architecture: "John Betjeman loved Albion Square," says Sinclair, laughing, "Or so I subsequently discovered ..."

He need not have worried about tweeness. During the Eighties, the council block at the end of his garden "became a crack barracks. Dealers took the flats, and you could see queues of people. It was like a pharmacy on the top floor. Then the police would steam in with sledgehammers." Wasn't he scared? "You were constantly being burgled," Sinclair says undramatically. "People would climb over the garden wall, kick in a door and grab a TV. Whether there was anybody in or not."

Such social entropy is the fuel of his fiction. Sinclair's books are splashed with graffiti, pub brawls, buzz-cut thugs and bent policemen. He is not a fearless observer - "I'm picking at my own scabs of horror" - but his courage swells mightily from pavement to page. Sinclair's sentences are short, masculine as Chandler. They strut.

This kind of confidence is, perhaps, the prerogative of London writers born away from the city. Celine's London Bridge is one of Sinclair's favourite novels; he himself comes from Wales. Maesteg was just a strip along a valley, but its dirty close terraces were menacing and urban in Sinclair's imagination. His father was a Scottish doctor, "full of very dark stories". His mother's family were "aboriginal Welsh ... connected with this thing called a Marie Lloyd, which was a horse's head, dug up on New Year's Eve. Drunks and outsiders would go round from house to house with the head, and sing poetry to the people inside. They would have to respond; if they failed to, they had to let the `dead' in and give them drinks."

Sinclair left this at 13 for boarding school in Cheltenham, then university in Dublin. It was the early Sixties, and, primed by his childhood curiosities, Sinclair waded deep into the counterculture. He read Kerouac and Ezra Pound; looked for "city speed" in rare Polanski screenings; moved to London and tried to shoot visions in 16mm (back-garden productions at Albion Drive alarmed the neighbours); and finally won a commission from West German television to make a film about Allen Ginsberg's Congress for the Dialectics of Liberation at the Albert Hall. It paid for the house: "We went down to a hotel on Hyde Park, and this German guy tipped out this carrier bag of money on to the bed."

Sinclair stayed in his bohemian niche. "There's an unreformed residue of the Sixties in him," says Patrick Wright, a rival East End explorer, whom Sinclair mocks gently in print but praises in person. "If he hadn't gone to ground in an area where he could hang around cheaply, he would have to have made more compromises." But scriptwriting was not really a living: Sinclair got a few hundred pounds for rejigging a graphic novel that later filled cinemas as Conan The Barbarian. He tried teaching and hated it; he took a job as a parks gardener.

This gave him his first book. By the Seventies Sinclair was already writing poetry, notably the clotted epic Suicide Bridge, infatuated with grim Burroughs phrasing ("unclean beast defilements") and the era's favourite occult conspiracies. But the easy routine of municipal gardening - slow drives between parks, sandwiches in graveyards - allowed Sinclair to focus his fascinations. One churchyard surrounded St Anne's in Limehouse; as he worked beneath Hawksmoor's vast white symmetries, he began to find the church mysterious. "It is possible to imagine," he wrote in the diary that became an essay, then a poetic speculation called Lud Heat, "that he did work a code into the buildings, knowingly or unknowingly."

Once he started looking, Sinclair found no end of signifiers. There was Hawksmoor's fascination with Egyptology, his unbuilt plans for pyramids atop his East End churches, their riverside sites as if by the Nile, the whole area's history as a burial ground since Roman times - Lud Heat was a breathless book. For all its blinding shafts of imagery, though, wasn't it also rather credulous? Sinclair is ready: "If you want to look at the Hawksmoor churches in purely architectural or sociological terms, you can do that ... I'm only opening them up to the imagination. It becomes chilling when people believe deeply that the churches are to do with some occult system ... I don't, but it's not enough just to say they are buildings like libraries or town halls."

He is being restrained here. Sinclair's friends, and his books, are quicker to suggest he looks for "a gothic frisson" in his researches. After running Lud Heat off his own Albion Village Press in 1975, Sinclair began a book about Jack the Ripper. White Chappell, Scarlet Tracings was more of a novel, layered with modern characters and 19th century ones, in the manner also employed by a certain Peter Ackroyd (who later acknowledged Lud Heat as the inspiration for his own, best-selling novel about Hawksmoor). Sinclair's notion this time was that the Ripper murders were the grisly consequence of Victorian anxieties about prostitution. His writing bent to the task with a poet's compressed potency.

But there were two problems. Sinclair lacked a contemporary plot to parallel the back-alley horrors of 1888. And, in 1976, he didn't have the money to stay at home and write it. The solution for both was book-dealing. For the next decade and a half Sinclair had a stall, three days a week, in an antiques market in Islington. Selling Victorian and pulp-drama rarities was only half the job; the rest was "charging around, looking". His co-conspirators, and competitors, were manna for a novelist: former anarchists, fallen toffs, esoteric crooks and amateur visionaries, all criss-crossing England in search of mythical books.

These years of spluttering cars, of stout and swearing and shiftiness, marked Sinclair's writing. When White Chappell, Scarlet Tracings was finally printed privately in 1987, after a doormat of publishers' rejections and the lavish financial intervention of a wealthy bohemian called Michael Goldmark, it had a new spine of book gossip and dealers' machismo. Despite Sinclair's scorn for the "timid" swimmers in the media and literary mainstream, he still calls the Groucho Club "Groucho's", like its members do.

By 1991 some of them were beginning to notice his existence. Sinclair acquired a corporate publisher for Downriver, the 400-page culmination of all his 6am walks, his pamphlet gathering, his careful listening to Cockney workmates and madmen. In 12 linked stories he traced the Thames from Tilbury, still echoing with the relics of Empire, past Thatcherism's hollow triumph at Canary Wharf, and deep into Hackney, where her reign's losers and refuseniks huddled. For long stretches, Sinclair achieved his Dickensian ambitions. He produced Edith Cadiz, a nurse holed up in a crumbling hospital tower, teaching immigrant urchins English by day, prostituting herself to Labour councillors by night; and Dr Adam Tenbrucke, a German currency dealer and collector of Conrad, driven to muddy suicide at Wapping. In 1992, Downriver won an Encore Award of pounds 7,500; it was his first literary prize.

SUCCESS prompts questions about Sinclair's achievement. Unlike Pynchon, he has yet to give his brilliant storms of words compelling narrative form. He is not very good at endings. Written on the margins for so long, his books have had fans rather than general readers, who may be more critical. In consequence, perhaps, Sinclair remains closer to a roving, vivid intelligence like William Gibson than to his Victorian literary heroes.

Other limitations lie intertwined with Sinclair's strengths. His bubbling argot, his noxious atmospheres, his speculative plunges into the "black swamp" of the past - the refreshing originality of this could stall into self-parody. The hero of his last novel, Radon Daughters, was a one-legged police informer with "cheese culture skin" called Todd Sileen.

Then again, Sinclair recognises the risks of repetition and prurience. Self-mocking "Baroque realist" authors increasingly infest his books, scampering excitedly after shadows, with estate agents selling East End eerieness close behind. "I'm going to be doing a book of stories about a hack writer doomed to write about London," says Sinclair. "His whole ambition is to get away from the city, but he's always pulled back."

Radon Daughters breaks out for Oxford and the west of Ireland, and Sinclair proves almost as painterly with sunsets and mystic mounds as he is with gutters and rust. Besides, the teeming corruptions he sees in the city have their own energy and life. He is not happy to be sold as a pessimist: "The title of Lights Out for the Territory is not the idea of lights going out on London. It's about lighting out across the river, into this wilderness again, returning to a source of inspiration ..."

Sinclair can sound like a Victorian naturalist. His great-grandfather was one, walking the Andes without oxygen in the 1890s. Sinclair would like to follow him there, now his children have survived their local schools. So far, this infinite curiosity limits his appeal as a novelist - assuming that is what he wants to be. "It's too much for most people," says his friend Michael Moorcock. "If he took one of his many strands and made it into a book, that would be the one to break through for him." Yet there are still alleys to measure, hidden obelisks to locate. "Everything in my books is extremely practical," Sinclair says, surging on with his whisky towards midnight. "It's there - I can take you to the place." Time, perhaps, for the A-Z.

`Lights Out for the Territory' is published on 23 January by Granta, pounds 12.99