On the road of excess: Rose Tremain follows a migrant's progress in a bloated Britain

Born in 1943, Rose Tremain grew up in London and studied at the Sorbonne and UEA, Norwich, where she later taught creative writing (1988-1995). After working in publishing, she became a full-time author; her debut, Sadler's Birthday (1976), was followed by novels such as Letter to Sister Benedicta, and the award-winning Restoration (1989). Sacred Country (1992) won two prizes and Music and Silence (1999) took the Whitbread novel award. Her recent work includes the 2003 novel The Colour and, in 2005, her fourth story collection, The Darkness of Wallis Simpson; The Road Home is published this month by Chatto & Windus. Twice divorced, with one daughter, she lives in Norwich with Richard Holmes, the biographer.

From the highest storey of the Random House headquarters in Pimlico, hackneyed film shots lie at every compass-point. Turn one way and Westminster's turrets loom; another, and the Byzantine wedding-cake of MI6 stands tall. This is London, and Britain, from the top down. Across the boardroom table, Rose Tremain – somehow both funky and soignée in a green blouson jacket – explains why her new outsider-hero endures the same city, and country, from the bottom up. Literally. The migrant Lev's progress through a land of material plenty and emotional dearth starts in a subterranean cole-hole in Earls Court where he kips once off the bus from his Eastern European home. "As a child I used to be told not to go into this dark coal-hole space, so it was a forbidden area for me, always rather spooky and exciting," she remembers. "That was the image that gave me the character."

Dark, secret places – in history, and in consciousness – have always excited a writer whose 10 novels and four story collections match an awesome versatility of setting with an equally striking consistency of vision. Her protagonists may span a galaxy of experience, from the would-be transsexual Mary in Sacred Country to the courtly chancer Merivel in Restoration; from the exiled lutenist Peter Claire in Music and Silence to the moribund Duchess of Windsor in "The Darkness of Wallis Simpson".

Yet, like Lev the "Eastern European Everyman" of The Road Home (Chatto & Windus, £16.99), they tend to be outsiders who view strange worlds slant, and through the prism of their hidden troubles. Lev, driven by bereavement as much as by the need to find employment in a country where the welcome might be frosty but the door stays slightly open, joins the ragged but hopeful company of Tremain's watchers and seekers.

"Are they versions of me?" Lev's creator asks. "I have no idea. Perhaps I'm writing the same book over and over again. They're often about journeys. They often have a bleak middle movement, to use an orchestral term, and then a kind of absolute or partial restoration happens towards the end. Perhaps the very journey of the novel presents itself in that way unconsciously to me, again and again. It's perhaps also something to do with honesty," she adds. "With wanting to see – whatever the world is, whether it's 17th-century Denmark or 2007 Britain – through eyes that are not too distorted and cloudy; too see in quite cold colours."

Those cold colours show Britain and the British in a largely – but not exclusively – harsh light. Via the sweat of his brow and the strength of his will, Lev slowly rises in the world from his underground bunker. He gets to know chefs and musicians; artists and playwrights and therapists; he loses his dearly-bought gains, then starts all over again. "Cities are fucking circuses," his best mate Rudi tells him, their friendship sustained across the sea through mobile phones. "And people like you and me are the dancing bears. So dance on, comrade, or feel the whip."

Curious, baffled, angry, honourable, rash and passionate, Lev is a tremendous creation, inhabited by his begetter to a depth that passes beyond empathy and into identification. Although he is a 40-plus widower and father, with burdens of memory and guilt at his back, Tremain compares him to Voltaire's Candide: "He knows very little about us, so he has the potential of being surprised by everything he finds". After all, " the book is also about us, not just about him. It's a mirror."

In that mirror Tremain shows the punishing nightly round of a smart London restaurant kitchen; the simple kindness of other migrants, Irish or Indian or Greek; the gruff benevolence of a Suffolk asparagus farmer. To research this part, she talked to Polish women workers on a Suffolk farm, where her presence proved "a great source of mirth". Why? "Our language was insufficient to accommodate that question, but this laughter was like the chatter of birds around me, which was very sweet". Lovingly-evoked food fills the novel, as so often in her work. Every meal – from tea-and-toast to Michelin-rated banquets – may mark the state of a mind, or the state of a nation.

The Road Home's mirror also reflects some unflattering British shapes. It skewers the character-twisting distortions of celebrity culture; the infantile greed, materialism and success-worship of so much contemporary life. Sophie, the sassy, sexy and generous colleague in the modish kitchen of "GK Ashe" who becomes Lev's lover, forsakes him in the end for an up-and-coming BritArt git. "They didn't used to be like this, but now they are," says Lev's stalwart, tea-brewing Irish landlord, Christy, about these result-fixated modern "Brits". "If you can't get your ball in the back of the net, you're no one."

The author shares Lev and Christy's dismay at a culture of excess. "I don't feel happy about where we are...I don't feel happy about this bloated, pot-bellied, slouching world that we inhabit." Lev expects to find the English thin and straight, like Alec Guinness in Bridge on the River Kwai; not roly-poly adult "babies", stuffing their gobs on the Tube. "We have got into this very over-sized world, and I don't feel comfortable with it". In The Colour, Tremain contrasted the long-term investment of the farmers in 19th-century New Zealand with "the terrible strivings and scramblings of the gold-seekers. And I think we're all on the gold trail now. "

The Road Home on occasion switches from saddened critique into Swiftian satire. The follies of conceptual art and avant-garde drama both draw raking fire. Tremain recalls seeing a degree show at the Slade in which a graduand had – after three years' work – painted a wonky line down the gallery wall and across the floor. "I felt a kind of sadness for the student, and I felt furious with the tutors. This is just too much. This we will not take." At the Royal Court, Lev storms righteously out of the press night of a fashionable shock-fest laden with viciously-parodied scenes of cruelty and abuse: "It's probably my age, but I just feel weary with it."

Yet Tremain is herself a proud child of the rule-busting, bourgeois-baiting Sixties. Although "shocked" by the "too-muchness" of the Noughties, she does point to the links that bind her own formative decade to this one. "I now understand that there was a selfishness in the way we all behaved in the Sixties, but we didn't think it was about self; we thought it was about communities." For all her fond memories of a Fifties childhood of deferred gratification, when "I wasn't allowed to have a chocolate biscuit until I'd eaten some bread and butter", Tremain has her share of mea culpa moments. "I am part of this culpable baby-boomer generation, who did move away from that into something much more self-gratifying."

Still, back in the laid-back Sixties and their aftermath, "I didn't have to have such a gigantic mortgage, or aspire to drive a smart car or wear designer clothes. All these things are pressures on young people now. This is the world of 'too much' that Lev comes into." Comes into, and moves beyond. The Road Home does steer its hero back towards "a cautious salvation". Somewhere between Baltic and Balkans, his ex-Soviet backwater remains, deliberately, a composite. Here the author's flair for sheer invention can flourish. "In the writing of novels," she says, "if I leave myself with nowhere to go imaginatively, I get completely bored... There has to be some area of the unknown."

Tremain's own patch is far from unknown. Famously, she has for 15 years lived outside Norwich with the biographer Richard Holmes. Every profile recounts the way the couple separate after breakfast for a hard day's work before their evening rendezvous. "That breakfast is always around 10 o'clock," she admits, lest her advocacy of a Puritan work-ethic sound a bit severe. "But that day-after-dayness is something I'm really used to. " The Road Home feelingly evokes the joy that well-made crostini bring to exhausted kitchen staff at the end of a shift. "The wonder of a small reward after a long day or night's work," purrs an author who happily says that "I'm never not writing something". " Writers, perhaps, appreciate this more than anybody."