London Orbital by Iain Sinclair

The visionary bard of London literature has left the East End to tramp around the M25 and its odd environs. Nicholas Royle relishes a journey to the verge of a cultural breakdown

The M25, its ribbon snipped in October 1986 by "Margaret Scissorhands", is described in Iain Sinclair's latest half-crazed ramble as "a security collar fixed to the neck of a convicted criminal", "an asteroid belt for London's rubble" and "a reason for staying at home". As for staying at home, Sinclair has done anything but. In the two years leading up to the millennium, he conducted a series of hikes around the fringes of Greater London that, when joined up, represent a shadowing of the halogen necklace that is the M25.

For every teeth-gritted tramp along the hard shoulder, there would be a corresponding stroll into the vanishing perspectives of a numinous Green Way. Detours were embraced, albeit mostly on secondary visits. Companions included a ragbag of Sinclair loyalists such as the artist Renchi Bicknell, whose shamanic agenda required him to pick up stones along the way for use in mysterious rituals, photographer Marc Atkins, writer and filmmaker Chris Petit (author of The Hard Shoulder), and journalist Kevin Jackson (saddled with the nickname Moose).

Sinclair, with his outpourings of East End verse, his quintessential Whitechapel novels, and his tireless compendium of metropolitan walks Lights Out for the Territory, has become synonymous with London literature. His last novel, however, was set in Wales, and London Orbital, (title notwithstanding) takes him from town to country, or what passes for it in the interzone between urban and rural. At first glance, it's tempting to rush to the conclusion that Sinclair is straining at the leash, his heart apparently set on this reverse commute. But it's impossible to consider the M25 and ignore that which it contains. Consequently, London Orbital turns out to be as much about London as any of his previous work.

"The 'story', if there was a story, had moved away from my old Whitechapel midden, from the river: developers and visible artists, explainers, exploiters, had taken care of all that," Sinclair writes. After London, then – London. (Richard Jefferies, whose 1885 fantasy After London occupies a slot in the metropolitan canon, is name-checked: one among many.) Bill Drummond – the writer, conceptual artist and former member of KLF who also shares in the legwork here – asks why the chosen direction is counter- clockwise. Sinclair's reason is to do with Italianate towers, "the only surviving markers of hospitals and factories. Our walk is a way of winding the clock back."

It soon becomes clear that land use around the rim – "perimeter land" – fell and continues to fall into distinct categories: hospitals, golf courses, industry, landfill and government institutions "Keep Out"). Mental hospitals are especially plentiful: "Asylums haunt the motorway like abandoned forts." Mostly closed and in some cases flattened, these outposts supported entire towns that have lost their way since the introduction of care in the community. Where they have been razed to the ground, the asylums have been replaced by Barratt homes. Gone are the schizophrenics and amnesiacs, their place taken by estates with no memory.

"Nagging away, at the back of our orbital walk, were recurrent themes, unsolved puzzles." Such as the Millennium Dome. Why? And how? New Labour comes in for a pasting: "Byers epitomised the New Labour attitude of glinting defiance, sitting bolt-upright in the back seat of a ministerial limo: a top-of-the-range cryogenic model of The Public Servant."

Sinclair's bile, always welcome, is not reserved for politicians. Of Box Hill he writes: "My feeling is that anywhere with a 'servery', anywhere that is 'partly open', is to be avoided. Why let someone else nominate sites that are worth visiting? Don't take my word for it, don't bother with my list of alternative attractions: Junction 21 of the M25, the Siebel building in Egham, Hawksmoor's gravestone in Shenley; discover your own."

This is the key to Sinclair's approach. It's why the text is not encumbered with directions, lists of buses, opening times. This is about as far from a guidebook as it's possible to get. The walking is an end in itself. Walk far enough and you'll enter a fugue state, like the Bordeaux gas-fitter Albert Dadas, who covered 70km in a day. "The fugue is a psychic commando course that makes the parallel life, as gas-fitter, hospital carer, or literary hack, endurable."

The writing is lucid, accessible, inventive and witty ("a suspicion of women"; "an irritation of flies"). It is to Landor's Tower what Lights Out ... was to Downriver. While Sinclair the novelist revels in his challenging fusion of vision and narrative – come and have a go, if you think you're clever enough – the rambler's speculations meet the reader halfway and are, ultimately, just as satisfying. London Orbital is very nearly worth 25 quid for this description of a pub fish lunch in Corbets Tey alone: "A grit of breadcrumbs dressing partially de-iced sog". Get your hiking boots on, even if only for a walk down to the bookshop.

Nicholas Royle's latest novel is 'The Director's Cut' (Abacus)