He gets used to London's rumbling grey autumn days. Instinctively turns up his collar as he emerges from the fug of the Tube into the damp cool of the streets; one in a crowd of muffled coffee-cup carrying commuters. It takes him a few months, but soon he prides himself on his grasp of the city's hunker-munker geography – no avenues and cross streets here – and navigates easily from meetings in features editors' glass and white gloss offices to long liquid lunches in nicotine-stained Soho bars; ducking down back alleys and shortcutting across squares.

He takes work as a freelance journalist; a once-young gun-for-hire. He writes cute culture-clash columns for Sunday magazines. He writes earnest reviews of new fiction for a broadsheet newspaper. He writes wry profiles of bright young things, iconoclastic playwrights and ground-breaking digital artists, and considered interviews with revered novelists and renowned actors. He meets his subjects in the antiseptic opulence of 5-star hotel lobbies; atmospheres all too familiar from his previous New York existence.

Once every three months, he takes the Hammersmith & City line to his agent's offices where Angela updates him on the backlist sales for Inside (steady enough for a three year-old book) and the follow up novella which was going to establish him as the new DeLillo (still sunken without trace). Each time she asks him what he's working on at the moment; drops hints that the time-window for another Upper East Side exposé has not yet passed with the public. Each time he shrugs and smiles in reply; sorry, he's got nothing.

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He meets up with Jenny every couple of weeks at the old fashioned Italian coffee house down the road from her studio space. She's a blast of vivid kinetic energy in his papery, inky existence. Jenny loves London, loves her life here. Loves the career she's carving for herself among its street-smart punk-spirited fashion scene. Loves that the friends and collaborators she's gathered about her admire her for her talent and her determination, not her zip code or the name embossed on the soles of her shoes. She smiles easily these days, beneath natural blonde bangs and lightly kohl-ed lashes. Still teases her brother as much as ever for his social awkwardness, his tendency to over-analyse, but her jibes are laced with generous and genuine affection; a desire to fill his soul with the same kind of creative fire that lights her own.

He's sometimes so proud of his little sister, for the success she is engineering on her own terms; for her poised self-assurance; sometimes just for the sparkling lightness of her laugh; that he has to blink back tears just looking at her. Of course, the instant she spots such ridiculous fraternal frailty, she morphs seamlessly back into the merciless mocking teenage version of herself, "God, Dan, what's wrong with you? You are such a girl!" He bats away the sachet of sugar she throws at him and laughs along with her. Later, on the way home, he wonders when it was that the gnawing hint of envy took root somewhere alongside his brotherly pride.

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He learns to enjoy the subtle shifts between the seasons here. Winter's grasping grimy fingers slip slowly away with each gentle breath of shy Spring. He spends six weeks undercover in the City investigating stock market corruption. The resulting article is published by The Economist and sees him nominated for the Bevins prize. Suddenly he's somebody again.

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He meets Freya at a book launch for a debut novel he's reviewed for The Guardian. She has almond eyes, honey blond hair and worked on the UK publicity campaign for Jeffrey Eugenides' latest novel. After four months of British-style dating – an after work drink (or seven), followed by the inevitable early morning walk of shame across the slumbering city - he moves into her Camden flat.

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Oddly, the one who keeps in touch is Chuck. After his marriage to the eldest daughter of the Earl of Elgin and the purchase of a Scottish castle, the former enfant terrible of the Upper East Side spends a significant part of the year on the European side of the Atlantic. Whenever he's in London, Chuck calls and they meet for cocktails at somewhere appropriately old-school; Claridges, the Ritz, sometimes the Savoy. Chuck keeps him up-to-date with Congressman Archibald's latest step on the long road his family fervently hope will lead to the White House, and fills him in on the current marital states of the various Van der Woodsens' (Eric happily settled with Sean, Lily dating a cosmetic surgeon - reverting to type since the divorce, Serena on husband number two – this one a sandal-wearing internet billionaire from Silicon Valley). It's a strange entente cordial that has settled between them, but it's sincere enough. He finds he enjoys Chuck's company now there's nothing either has left to play for. There's even enough water under the bridge for Jenny to join them on occasion; after all it was Chuck's initial investment that allowed her to start up her own small fashion line. A decision that was simply good business according to Chuck, given Jenny's rising star, but simple absolution to the Humphreys.

When Chuck's invited to a weekend shooting party in the English countryside he asks Dan to join him, in need of an American comrade-in-arms. Even in head-to-toe tweed there's no mistaking a Bass out of water, and he's both amused and relieved when Chuck makes their excuses after fifteen minutes of ferociously erratic aiming at non-existent grouse and they retreat back to the house's extensive library and equally extensive drinks cabinet to re-establish their colonial superiority.

In all their meetings they never once mention her. It's an unspoken agreement between them, but no less binding for that.

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The rumbling grey autumn days roll around once again and settle their weight around his shoulders like an old overcoat. He makes the trip to Angela's offices, shrugs and smiles in the usual places and pretends not to hear her sighs of exasperation. Each time the royalty check she hands him is a little smaller than the last.

Freya invites him to spend Christmas with her parents. He experiences a raw wave of guilt as he waves Jenny off at the airport; his presents for Rufus bundled in among her luggage. He passes the holiday in his girlfriend's large red brick family home, which nestles unobtrusively behind a row of privet hedge in a typical middle-class Berkshire village; three-thousand miles and a whole world away from the Brooklyn loft and another universe entirely from the Van der Woodsen penthouse. He's charming and witty to Freya's mother; serious and manly with her father; and exchanges knowing winks and contraband cigarettes with her brothers. Freya demonstrates her delight with his performance every night in her childhood bedroom, a bank of teddy bears forming an uncomfortable audience.

At a quarter to midnight on New Year's Eve he calls Chuck in New York. Through Chuck's shouts over the noise of what sounds like quite a party, he learns that Chuck is seeing in the New Year with Anne-Marie, a United Airlines stewardess, while his wife celebrates the same turn of the clock at the Scottish castle with Sir Robert Eaton, the husband of one of her old school friends. Chuck sounds more sanguine about the situation than Dan would in his place, making much of his relief at being spared another year of bagpipes and choruses of Auld Lang Syne, but it was ever thus.

"Well, countdown's started. I'd better find Freya. Good to speak to you. Happy New Year, Chuck." "Same to you, Humphrey," replies Chuck in a rye-soaked voice. The strange thing is, it strikes him as he hangs up, they both mean it.

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In February in an old packing warehouse in Covent Garden, Jenny shows a small collection for the first time at London Fashion Week. The front row isn't thronged with wall-to-wall A-listers but enough of the right people are there to ensure the message gets out that Jenny Humphrey is a talent to watch. In among the fashionistas, applauding more loudly than anyone as the designer takes her bow, are three slightly incongruous figures. Rufus is fit to burst with parental pride from the moment the first model takes to the runway to the sound of an early Lincoln Hawk track. Chuck pretends to be there purely to reap the rewards of his investment foresight… and to pick up models. And as for him, well, he's just glad that one Humphrey is living up to their potential.

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She flies into town for Fashion Week, naturally, but the world would have to spin off its axis before she took a seat at a Jenny Humphrey show. The fashion weeklies carry shots of her on the front row at Christopher Kane, head high, expression unfathomable. He flicks through the copy Freya leaves in the lounge and pretends not to notice the photographs.

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In early spring, Freya comes home with news that her publishing house are looking to commission a new biography of Richard Yates. She knows she should have spoken to him first but it sounded like such a great fit that she put his name forward to the commissioning editor. He jibs at the loosening of yet another link in the rusting chain of control over his own destiny, making Freya call him an ungrateful wretch, but thinks nothing more of it. Two days later he gets a call. Two weeks later he's in Boston sifting through Yates's archive papers.

The book takes a year to research and six months to write. He spends long periods in the States. Sometimes he stays in Brooklyn with his dad for a few days each side of the trans-Atlantic crossings. Rufus is almost pathetically grateful for his company on these visits. The loss of two great loves, Alison and Lily (twice), has taken a toll. He always seemed younger than his years when Dan was growing up, almost more of an older brother figure than a father. Rufus seems old to him at last. He didn't know loneliness could seep into people's bones, making them brittle.

On one occasion he's staying at the loft when Serena appears; uninvited, unexpected. Husband number two is about to become ex-husband number two and so she's back in Manhattan, for now at least. She's still beautiful, lithe and buxom; but the golden sunshine that used to illuminate every room she walked into has dimmed, become a little brassy in its sheen. The skin around her mouth is tighter, more Lily-like; her child-like peals of laughter more forced. They drink beer from the bottle by the river at Brooklyn Heights, Serena waxing nostalgically about days gone by as if they were still friends, as if they might yet be lovers. She smells like bourbon; warm, sweet and heady; that quality she has that makes every lonely man think he's found his reason for living. But he's not that kind of lonely any more. When Serena rests her head on his shoulder, her intoxicating blonde cocktail only makes him feel tired. She asks him what's wrong. He has no idea where to start, so instead he shrugs and smiles; sorry, he's got nothing.

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When he returns to London to write, the home dynamic has changed. Freya is alternately clingy and needy, or irritable and distant. Over dinner one night when she's being particularly intractable, she asks him where he thinks their relationship is going. It's so predictable a question he has to swallow down his disappointment. Instead he asks her where she would like it to go – which after all seems more to the point. She avoids a direct answer in a thoroughly British manner, playing with her food as she mentions all the friends' weddings they've been to recently and how many new baby cards she's had to buy in the last few months.

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On a rumbling grey autumn day he submits his biography of Yates to his editor and asks Freya to marry him. Her almond eyes fill with tears as she kisses him and whispers, 'yes', and he wonders if anything will ever really happen to him again.