A lore unto himself: Owen Sheers is having his way with an ancient myth

There is something incongruous about interviewing Owen Sheers amid the rooftop haunts of Piccadilly. Sipping mint tea, blue-eyed and improbably boyish, he sits perched in a private room on the forelock of the old Simpsons building. With its metropolitan solidity and Art Deco twists, this one-time gentleman's outfitters and now flagship Waterstone's store is a resolutely urban environment in which to meet a writer so indelibly linked to the rhythms of the rural Welsh countryside.

Sheers has two new books published this month, both distracting him from his position as one of Britain's most promising young poets. The first, A Poet's Guide to Britain, accompanies his BBC4 series in which he takes part in "a particularly vital conversation between Britain's poets and her places". The second lashes the past to the present through a contemporary take on one of the 11 stories of the Welsh Mabinogion myth cycle. The result, White Ravens, is "a story both of its time and yet timeless, part of its colour being leant by the temporal lens through which it is read". Sheers believes that both books inhabit "shared territory". This is particularly true in how they revisit familiar tales and verse, illuminating them to new effect.

As we talk, London stretches out in front of us. In the closing tenor of a late autumn afternoon, the skyline peaks and troughs with the church spires and light-struck gaps of thoroughfares, sketching the horizon like a faint polygraph result. Similarly, in A Poet's Guide to Britain, Sheers captures the various highs and lies of the city through a textual domino topple, as one poem connects with the next. In "Piccadilly Circus at Night", DH Lawrence finds Eros sitting in the "asphalt isle in the sea" where "we hard-faced creatures go round and round". Gloomy stuff, but he's followed by Laurence Binyon, who finds a positive undertow to the city: "A sudden consolation, a softening light, touched me: the streets alive and bright, with hundreds each way thronging, on their tide."

Sheers' thesis is that the landscape of Britain can be heard through a set of discordant voices. "I felt as if I were putting my ear to an atlas of the country," he claims in his introduction to the volume. The book evolved out of the television series, a realm that Sheers previously encountered as a Big Breakfast researcher in the 1990s. He clearly has mixed feelings about the medium. "Once you put your face on TV, people think you're loaded. If it's with BBC Four, I can tell you now that you're not," he laughs.

Born in Fiji in 1974, Sheers' adoptive Abergavenny was to provide his primary inspiration: the landscape and heritage of South Wales. The Blue Book, his 2000 debut poetry collection, found him chronicling farm life and familial loss and shot him into the public gaze. He has since written Skirrid Hill (a second poetry collection), The Dust Diaries (a semi-fictional biography of a distant relative who set out for a missionary's life in Rhodesia) and a novel, Resistance, in which he imagines a border valley riven by moral dilemmas when German troops arrive in 1944. The fluctuating levels of clarity inherent in both folklore and personal history shape most of Sheers' writing.

In White Ravens, he draws on "Branwen Daughter of Llyr", the second story of the Mabinogion (pronounced in Welsh as mab-in-og-eee-on) for his Second World War tale. Matthew O'Connell is an Irish volunteer assigned to a shadowy unit entitled the Underground Rumour Mill, from which he distributes shifty tales intent on undermining Nazi morale. He is sent to a remote hill farm in Wales to collect raven chicks for the Tower of London, legend dictating that if the birds die out, the nation will fall. However, it's in the discovery of true love that Matthew finds conflict brewing.

The Mabinogion, explains Sheers, is as much a part of Welsh culture as the Arthurian legend is in England. However, he's keen to emphasise that all of these myths drift in and out of the fog of our consciousness. "That's why this was a particularly interesting project. They were originally written down in Welsh in medieval manuscripts and obviously they are thought of as being Welsh myths. But I see the most ancient myths of the Mabinogion as really being ancient British myths, as they happen before there was an England, Wales, Scotland." The divide exhibited in many of the stories, including the branch on which Sheers has based his novella, concerns that between this "common land" and Ireland. As such, the tale can be seen as "a Welsh-Irish Romeo and Juliet".

The most intriguing aspect of Sheers' take on the myth is the official sanction of mythology, through a government "investing in superstition". The use of the bizarre raven mission is a typical authorial tactic for Sheers, combining the ancient with the contemporary, the real with the imagined. "Truth is stranger than fiction. What really happened was that there were only a few surviving ravens so they were moved to a farm, I think in Norfolk. But what was kept secret was that they had to be moved. And the secrecy notice on that has only just been removed, whereas the secrecy notice on the Enigma machine was removed over 30 years ago."

Sheers believes that "contemporary Welsh writing is in a very healthy period". To complete these new takes on the four original branches of the Mabinogion, the Welsh publisher Seren Books has also assembled the talents of Russell Celyn Jones, Niall Griffiths and Gwyneth Lewis. All were invited to update in any form they wished. "That response could really take any shape," says Sheers. "I'm sure we all thought, 'Oh my god, I must bag my myth before it goes.'"

I suggest that his writing and presenting (he is about to film a new series on the sea's place as muse) connects with the current obsession with the natural world's impact on British heritage. He insists that it wasn't a conscious aim but is happy to be associated with a trend that includes the bestselling travelogues of Robert Macfarlane, Roger Deakin and Kate Rew and the small-screen successes of Coast. "More and more of us are living in urban conurbations," says Sheers. "Perhaps there is a real hunger to feel the proximity of the natural land, even if it is at one step removed." His poem "River Swimming" captured the essence of what we miss in our municipal constraints: "Feel the fish kiss the hairs on your leg. Then push through to the promise of liquid sun." He even confesses to having just taken an October dip in a tarn with Sarah Hall: "Absolutely bloody freezing but great."

Sheers is currently torn between town and country. "I don't really have a home at the moment. It would make all sorts of sense to be based in London," he says, eyebrows raised in mock despair. Then he smiles and admits to an "incredibly strong desire to just go and buy that cottage in the Black Mountains".

He worked on both books during a two-year stay in New York from which he only recently returned. His possessions are still in transit. He left for Manhattan to take up a Cullman Fellowship in the New York Public Library. It was, he acknowledges, an "amazing" environment. "It's like someone has placed you in a room with 14 of the people you would most like to meet in New York, to talk to and learn from. You also get complete access to the manuscripts, archives and special collections. It's a very strange nine months. You can look through Dylan Thomas's wallet, you can pick up Virginia Woolf's walking stick. I'm sure it's going to feel like downhill from here on in."

The poetry scene in the US lacked the educational values, through state-school readings, which remain important to Sheers and many British poets. "When I teach kids, one of the ways I get them enthused is to say, 'At the end of this workshop, whatever you write, however good you think it is, or not, from the same 26 letters that we all use all the time, you will have actually created something that has never existed before in the history of mankind.' And then they go, 'Aaahh...'" Once again Sheers finds himself broadening horizons.

'A Poet's Guide to Britain' is published by Penguin Classics, priced £20

The extract: White Ravens, By Owen Sheers (Seren £7.99)

'...When Matthew drew back those curtains the full extent of his isolation was revealed to him, in all its drama. A long sweep of cleanly sculpted mountains curved away from the farm on either side, like two huge waves rushing together, a maelstrom stilled just moments before collision. Between these mountains, smaller hills and hummocks of moorland echoed each other into the distance'