All the secrets of the streets

<i>London: the biography</i> by Peter Ackroyd (Chatto &amp; Windus, &pound;25, 779pp)

Kingsley Amis's Memoirs record how the novelist was rung by his friend John Braine to hear news of a change of address. "I'm resident in London now lad," revealed Braine, formerly located in his native Bradford. Excellent, Amis enthused, envisaging bus-rides or brisk walks to the Braine domicile: where exactly in London? Braine had moved into a flat above a mini-cab office in Woking. In much the same way, the chorus of Sham 69's punk classic "Hersham Boys" ran: "Hersham boys, Hersham boys/ They call us the cockney cowboys". Hersham, as perhaps even the most charitable A-Z compiler will allow, is in Surrey.

Kingsley Amis's Memoirs record how the novelist was rung by his friend John Braine to hear news of a change of address. "I'm resident in London now lad," revealed Braine, formerly located in his native Bradford. Excellent, Amis enthused, envisaging bus-rides or brisk walks to the Braine domicile: where exactly in London? Braine had moved into a flat above a mini-cab office in Woking. In much the same way, the chorus of Sham 69's punk classic "Hersham Boys" ran: "Hersham boys, Hersham boys/ They call us the cockney cowboys". Hersham, as perhaps even the most charitable A-Z compiler will allow, is in Surrey.

So where is London? Where does it begin and end? And what is a Londoner? For something so concerned to offer up characterisations of the city - variously described as a "prison", a "furnace", a "swamp" and a "repository for lust" - London: the biography is oddly short on definitions. Barking gets a mention, and there are occasional references to Streatham and Upper Norwood, but the resident of Putney or Crouch End who wonders how he and his forbears fit into this sprawling meditation on London's history will go away disappointed.

You can see Peter Ackroyd's point: 150 years ago, Putney was largely unbroken countryside, while Hammersmith was known for strawberry fields. The continuities and twitches on the mythological thread that Ackroyd seeks in this quarter-million word patchwork of echoes tend not to be found outside the Circle Line, but in the city's ancient heart. Neither are they immediately apparent. As the introduction puts it, "The readers of this book must wander and wander. They may become lost upon the way; they may experience moments of uncertainty, and on occasion strange fantasies or theories may bewilder them."

If the foregoing sounds a touch whimsical - and uncomfortably close to the kind of sub-romantic glosses offered by H V Morton, to whose In Search of London (1931) Ackroyd refers - then it should instantly be said that what follows is by no stretch of the imagination a conventional history. Although Ackroyd opens with three or four chapters of pre-Elizabethan chronology, these are the dullest parts. As one might expect, given the fixations of previous Ackroyd outings such as Hawksmoor (1985) or his biographies of Blake and Dickens, the narrative - such as it is - only starts to pick up in the early-modern era.

The remaining seven-eighths, divided into 70 or so mini-essays, supply a huge, unstoppable torrent of detail (the London mob, low-life, cookery, speech) in which the figure of the author can be seen wandering about - like one of the scavenging boatmen of his Thameside chapters - in search of pattern and design.

Ackroyd's great theme is continuity, closely followed by relativity. "In this city everything connects," he writes. Milton is quoted to the effect that "oft-time relations heretofore accounted fabulous have bin after found to contain in them many foot-steps, and reliques of something true."

Time's arrow turns up many suggestive conceits. Speculating on how Pentonville got its name, Ackroyd is forced to acknowledge the claims of the Mr Henry Penton who first developed the area, while pressing the possibilities of Druidic survival ( pen being Celtic for hill, ton deriving from spring). There are similar points about Billingsgate (the Celtic king Belinus or plain Belings, who owned the land?) and Ludgate.

Without wanting to cork these imaginative outpourings, there is perhaps a limit to the usefulness of "organic continuity". Ackroyd discovering that the inscription on vintage sewer covers, SELF-LOCKING, has worn away to ELF KING is one thing; but the city as a living entity can begin to irk. Thus we learn that the city "suffered periods of weariness and enervation when the spirit of the place hid its head".

Discussing metropolitan murder - some predictably blood-curdling stuff on offer here - Ackroyd notes that it was "as if the city itself might have taken part in the crimes". The streets and houses in the vicinity of the Jack the Ripper murders became associated with them "almost to the extent that they seemed to share the guilt". As for the hordes of 18th-century poor, "it was as if the streets themselves had engendered these huddled masses". You can't help feeling that economic conditions played their part, rather than autogenesis beneath paving stones.

An occasional urge to rein in the more exalted flights of "vision" on display here may seem an unnecessarily prosaic response. To a considerable extent, this is a London lit, if not by lightning-bolt, then by the link boy's flaming torch. The smell of metaphorical greasepaint hangs in the air. Many subjects of Ackroyd's previous books - Nicholas Hawksmoor, Dan Leno, George Gissing - are here, and many of the symbols too: light, shade, birds caged, birds in flight, water running.

As in the better of his novels, the best effects come via a combination of magpie antiquarianism and sheer descriptive drive. Among the former, an obscure museum off the Walworth Road turns up a collection of amulets, including a grey cat's skin used against whooping cough. Among the latter, Ackroyd's accounts of - to pick only a handful of highlights - the Plague, the Great Fire, the Gordon Riots of 1780 and the Broadwater Farm disturbances of 1985 are wonderfully sharp, and printed with the usual patterns. A characteristic of both late 18th- and late 20th-century riots was the allegation that unknown orchestrators fomented the violence.

It would be surprising, given his track record, if Ackroyd were not disproportionately attracted by the violent, melancholic and pavement-to-gutter aspects of his subject. In general, the genteeler sides of bourgeois diversion and gentlemanly splendour take a back seat. One could also have done with more on "Bohemian" London and the great Soho/Fitzrovian tradition of sponging artists and drunken hacks.

Not much, either, on the dystopian capitals imagined by everyone from Richard Jefferies to Chesterton, Wells and, more recently, Ronald Wright, whose A Scientific Romance (1997) contains an eerie vision of sprouting jungle seen from the top of Canary Wharf. In the end, though, even allowing for many idiosyncrasies of method, London: the biography merits the description Ackroyd attaches to one primary source, Charles Booth's Life and Labour of the People in London (1903): "A monumental work: it is full of suggestive details, and suffused by a curious pity".

D J Taylor's life of Thackeray will be published by Pimlico