Seamus Heaney, photographed in Dublin, 2009. Photograph: Antonio Olmos

Seamus Heaney is taking a taxi from his home in Sandymount, which overlooks the bright grey waters of Dublin Bay, to the centre of town. Our driver is silent, but bursting with respect. When the poet compliments him on the ingenuity of his route through the lunchtime traffic, the cabbie exclaims, with a sudden loss of discretion, "Only the best now for Ireland's favourite son."

Everyone wants a piece of Ireland's first Nobel-winning poet since Yeats. When we arrive at our destination, an oyster bar overlooking St Stephen's Green, the ebb and flow of Irish pride in Seamus, as he is universally known, surges up in a succession of spontaneous greetings. Everyone recognises Heaney's professorial spectacles and silvery mop.

A frisson passes through the restaurant. This woman wants to tell him about her daughter, recovering from leukaemia, and to ask for an autograph. Two punters, checking the starting prices on a laptop, volunteer a tip about the 2.30 at Leopardstown. Another old chap wants to be remembered. And the maître d' is beside himself with getting the best table ready.

I wonder how Heaney can stand it.

No need to worry. The object of this attention seems to move in a serene bubble of modesty and unconcern: he likes the attention, and it does not really trouble him. He's had it, in different ways, all his life, and he knows that, for an Irish poet, it comes with the territory.

There are many ways to be a famous writer in Dublin. You can be mad and grand, like Yeats; or mysterious, like Beckett; or drunk, like Flann O'Brien; or absent, like Joyce; or what? A long time ago, Clive James nailed Heaney with "Seamus Famous", but that's a gag, at best half true, spun off Heaney's brilliant self-presentation. There is rather more to the poet than his fame, dazzling though that can be.

For someone who has been so remorselessly scrutinised, Heaney is still something of an enigma. He works hard to make "famous" seem normal. Unfailingly courteous and attentive, he can also be grave, remote and occasionally stern, always watching himself, like the king of a vulnerable monarchy.

In keeping with that vigilance, and a well-defended uncertainty, Heaney is always asking himself the essential questions articulated in Preoccupations, his collected essays. "How should a poet properly live and write? What is his relationship to be to his own voice, his own place, his literary heritage and his contemporary world?"

I've known Seamus Heaney for about half of his writing life. The key to our friendship was always a third party: the mischievous, antic figure of the folk-singer, broadcaster and lord of misrule, David Hammond, from Belfast. Last summer, after a long illness, Hammond died. I was in America at the time, and unable to go to the funeral.

As part of my farewell to "Davey", I knew I had to see Seamus, pay my respects to the dead, and share the recollection of old times. Quite apart from my deep affection for Hammond, I'm conscious that Heaney is keen on the proper obsequies (he loves funerals) and will be only too glad to raise a glass to our old friend.

It's a good moment. Heaney has just turned 70. On the table in the window of his attic study - the place that he calls his "hutch" - there are three piles of poetry books: he wants to pass on good first editions of his life's work to his children. As well as copies of the best-known volumes (Death of a Naturalist, North, Field Work, Door into the Dark and Station Island) there are the translations (Sweeney Astray, Beowulf), the plays (The Cure at Troy, The Burial at Thebes), and some very rare editions from small presses, an accumulated bibliography of between 30 and 40 titles.

With three score years and ten behind him, Heaney is in a quasi-mystical mood, ready to take stock of his life and to address the question of growing old as a poet. "The problem as you get older," he says, "is that you become more self-aware. At the same time you have to surprise yourself. There's no way of arranging the surprise, so it is tricky. You're either obsessed or you're surprised. There's no halfway house."

Lately, his age has given him both an extra reason to take stock and also a premonitory surprise, a sudden tap on the shoulder. In August 2006, Heaney had a stroke, something he's not spoken about publicly before.

Heaney and his wife, Marie, were up in Donegal for the 75th birthday of Ann Friel, wife of Brian, the playwright. "We flew up there," says Heaney, taking up the story. "There were many old friends. We all stayed in a boarding house, and went to bed at around 12.30." In the past, Donegal has been the scene of certain bardic revels, but on this occasion, he says, "it wasn't a wild night. David Hammond was there, Brian Friel himself. John Hume. Tom Kilroy [the writer], Desmond Kavanagh. I went to bed around one o'clock, and woke at eight the next morning. We were in a twin-bedded room, and I spoke across the gap between us to Marie, reporting a remark made to me the night before by Brian Friel about another distinguished Irish writer. You know, in the middle of the floor, he'd said to me, 'X is a real shit, you know.'"

Heaney goes on, "So we had a good laugh about this, and then I made a move to get out of bed, and I felt strange. I didn't know what was wrong with me. I made to move, but I couldn't move, and I felt very odd. My speech wasn't affected. When Marie came over to help me, she saw my leg was twisted, and she began to cry out. And I said, 'For God's sake, calm down.' Yes, I spoke roughly to my little girl, and then I realised there was something seriously wrong, so I apologised to her and said. 'Yes, you'd better go to the Kavanaghs.'"

This was a piece of luck. Mary and Desmond Kavanagh and their children are medics.

"So immediately the family went into action," Heaney continues. "The medical grapevine across the country was alerted and the ambulance was on its way. [The poet] Peter Fallon and Kavanagh carried me down the stairs."

Heaney reports his instinctive Ulster sang froid, saying: "My sense of humour was intact as they were carrying me down." Almost everyone involved in getting the bulky, 6ft figure of Heaney down the stairs had been involved with the Field Day theatre company, and many of the group had recently suffered minor illnesses. So now, with his natural detachment, Heaney made a joke. "It's the curse of Field Day, I said. But within an hour I was in the ambulance."

"The trip in the ambulance I always remember," he says, "because Marie was in the back with me. I just wrote about it three weeks ago. To me, that was one of the actual beauties of the stroke, that renewal of love in the ambulance. One of the strongest, sweetest memories I have. We went through Glendorn on a very beautiful, long, bumpy ride to Letterkenny hospital." There, they did a scan, he continues. "And the woman who was doing the scan - this is Ireland for you - the nurse said, 'I believe you were at Friel's last night.' Her uncle had been at the party. So this is Ireland," he repeats, with satisfaction. It's certainly Heaney's Ireland.

Heaney's stroke - the festive occasion; the circle of old friends; the jokes; the Irish grapevine; the observation of the self from afar; the country drive - is all of a piece with the poet's character, good fortune and his unflappable temperament. Within a comparatively short time, a matter of weeks, he was on the road to recovery. Looking back, he can even refer to his hospitalisation as "a rest cure".

But I've had my own experience of stroke. It is much bleaker than that. So I pressed him about the darker side of his experience. "Yes, I cried," he says. "I cried, and I wanted my Daddy, funnily enough. I did. I felt babyish." But the public Heaney cannot enjoy the luxury of self-indulgence. Even by his standards, the next stage of his convalescence was surreal, a visit from a friend, the former president of the United States.

"Clinton was here for the Ryder Cup," he says. "He'd been up with the Taoiseach [Bertie Ahern] and had heard about my 'episode'. The next thing, he put a call to the hospital, and said he was on his way. He strode into the ward like a kind of god. My fellow sufferers, four or five men much more stricken than I was, were amazed. But he shook their hands and introduced himself. It was marvellous, really. He went round all the wards and gave the whole hospital a terrific boost. We had about 25 minutes with him, and talked about Ulysses Grant's memoirs, which he was reading." Then Clinton was off, back to the airport.

Around this time, perhaps responding to the larger stage on which he always finds himself, he began to write a poem, Miracle, inspired by the gospel story of the paralysed man lowered through the roof into Christ's presence. Heaney insists that it's not a spiritual poem, but one that marked "being changed a bit by something happening. Every now and again you write a poem that changes gear."

He had never written a poem in response to scripture before, and says he is not a believer. But clearly the stroke had come as a powerful moment of punctuation in his intensely busy life, and gave him the idea that he should devote more time to himself. "I looked at the calendar after these days in the hospital," he says. "I thought, 'My God, you've never stopped, Seamus.' So, for a year afterwards, I just cancelled everything. I decided that in hospital."

So now there was another pressure, a new conflict to wrestle with. "I spend a lot of time saying 'No' to people," he says, "and then being anxious about saying No." He says his illness has heightened an inner sense of private doubt, confiding, "I'm less confident about public speaking. I spend a lot of time worrying about it, and getting it ready. I'm not good spontaneously at all. I suppose it's balancing a sense of obligation against self-preservation."

Meanwhile, in hospital, making a steady recovery, he read more than he had in ages, finding a special comfort in thrillers by Henning Mankell, Donna Leon and Robert Harris. With time on his hands, inevitably he also reviewed his situation. His mother had died of a stroke at 74, never regaining consciousness; his father from colon cancer at 76.

Did he, from his hospital bed, have any regrets about succumbing to the pressures of celebrity? "I can't regret myself," he replies. "I mean, it's part of me, for better or worse. I'm aware now that I've repeated myself, but it's my temperament. I'm stuck with it."

Seamus Heaney was born in 1939, just before the Second World War, on the farm of Mossbawn, near the village of Castledawson, County Derry, into an Ulster farming family. In one of his poems, he recalls a strangely tranquil haven from the storms raging across the west - the thump of a sledgehammer, and the "heavyweight silence" of cattle in the rain.

Mossbawn is equidistant from Derry and Belfast, in deep country, a one-storey thatched and whitewashed house set back from a main road, though the traffic was always intermittent. Heaney says that the dominant notes in Mossbawn were the clucks and cackles of the hens, and sometimes the roar of a calf or cow from a nearby field. He also remembers the screams of the pigs from the slaughterhouse across the way.

His mother, who was a McCann, gave him the convivial side of his character. "The Heaneys were more kind of native American," he jokes. "They were always in the wigwam, facing each other, and very grave. There was a kind of stoicism about the Heaneys and an Anglo-Saxon melancholy, and everything was very measured. Marie once said of them that they didn't carry a spare ounce of emotional weight. That was completely true."

To be crude about it, his McCann side nurtures his public face, while the Heaney part fuels the graver and more introspective reflections of the poetry. His wife Marie also tells me that Mossbawn holds the key to her husband. "It's his paradise," she says. "His Eden. All he's ever wanted to do is go back."

Both the McCanns and the Heaneys were Roman Catholic families in Protestant Ulster. This has placed him at the murderous crossroads of sectarian conflict and Irish nationalism throughout his life. It's an unenviable and dangerous location at the best of times, and there's a part of him that's highly attuned to the history and heritage of oppression. He has always moved, as he puts it, "like a double agent among the big concepts". On both sides of the border, some still question his loyalties.

"My mother's side," he goes on, speaking carefully, "were much more alert to the exacerbations of the situation, and with a stronger sense of injustice, and a more articulate mockery. The irony is so important. In the north, northern irony has allowed people to stand at the edge of the rift and shout across to each other. This is very important, actually. David Hammond used to say, 'Banter, banter is the curse of us all.'"

Life in Mossbawn, in the Ulster countryside, is what gives Heaney his language and imagery - words like "braird", "seggans" and "sned", titles like A Hagging Match, The Haw Lantern, and Broagh, a placename almost impossible for an outsider to pronounce correctly. I remember asking him about the nuances of Ulster English for a television programme some years back. Heaney's reply expressed not only a deep reverence for the sanctity of his country paradise, but also articulated the source of his creative energy. He remains, pre-eminently, the poet of the peat bog and the home fire. He said: "Your language has a lot to do with your confidence, your sense of place and authority." He added that speaking his own language, Irish English, was to acquire a trust in the pronunciation and in the quirks of vocabulary, and "to go through a kind of political re-awakening".

Heaney's poetry has a distinctive poetic language that comes from a direct and intimate connection with the Irish landscape and its culture rather than any academic literary ambition. He has often said that he showed no special aptitude or poetic promise as a child.

A poem like Alphabets recalls a small boy wondering over the alphabet, but showing no precocious mastery - "First it is 'copying out', and then 'English'" - until, as he puts it, "the poet's dream stole over him like sunlight." If there was poetry in Mossbawn, it came through holiday, festival and party recitations.

Then, in 1953, this paradise was shattered when his brother Christopher was killed in a road accident, aged three. In the elegiac poem Mid-Term Break, Heaney wrote about this dreadful episode in his young, adolescent life (he was 13). He describes being "embarrassed by old men standing up to shake my hand", and then, with the poet's detachment, seeing his baby brother's corpse laid out in an upstairs room with "a poppy bruise on his left temple". Even by the stoical traditions of the North, Heaney learned early to ingest his pain.

Young Seamus was the scholarship boy in a family of seven boys and two girls. As the clever, eldest one, he was bound for the city - the great Protestant industrial and shipbuilding inferno of Belfast. As a country boy, banished from Eden, he was lost. His first poems were written under the pseudonym "Incertus". He has described the personality of this pseudonymous poet as expert in obeisance, "a shy soul fretting. Oh yes, I crept before I walked."

"I was describing my own unsureness," Heaney explains, when I ask him about the Incertus pseudonym. "Describing exactly the inner state of the creature. When I was an undergraduate [at Queen's, Belfast], I was in the poetry-aspiring business, and I didn't feel confident. I didn't feel I had crossed any line. I was still scrabbling on the outside, not entering."

Heaney, who often harks back to the Anglo-Saxons, has many of their qualities. Behind his homespun bareness there's a highly wrought editorial process at work, and a good deal of artifice in which things are not quite as they seem. It's this that can sustain an accusation of deviousness and even cunning. In his own career, "Incertus" was soon replaced by "Seamus J. Heaney". This was the young man from Castledawson who, at the turn of the Sixties, began to experiment with poetry.

In the autumn of 1962, Heaney met young Marie Devlin, his future wife. "We met at a dinner. That evening I walked her home, and I lent her a book, saying I needed it back by Thursday. The disgraceful truth was that I had a girlfriend, and she was returning on Friday." It's a long time ago, but he is still rather sheepish about the memory. "So we met on Thursday, and then there was a kind of stealth. It took a long time to clear the decks. But there was a kind of immediate recognition, yes."

As well as falling in love, he began to write poems with "a new sense of possibility, and a new confidence". He protests that "they weren't any good," but remembers "I was excited." He had joined Philip Hobsbaum's influential Belfast poetry circle, a group, he once said, "who used to talk poetry day after day with an intensity and prejudice that cannot but have left a mark on all of us". It was within this circle that he first wrote poems such as Digging, Tollund Man, Mid-Term Break and Death of a Naturalist.

With an exhilarating sense of discovery and excitement, these early poems were published by Karl Miller in the New Statesman. Then Faber showed interest; everything was happening very fast. "I knew I wasn't quite ready," Heaney says, "but I wrote like hell and sent the manuscript in." That was January 1965. When he describes it now, it seems to him as if it was yesterday. "To be truthful, it wasn't until North was written, and had come out, that I felt I had followed a calling or done something in the name of it."

Death of a Naturalist was noted for poetry that sprang from the farming life of Heaney's youth, and its subtle communication of a physical and pastoral intensity in a language of profound and unforced simplicity. Heaney, whose work appeared at the same time as Thomas Kinsella, Derek Mahon, Michael Longley, Paul Muldoon and Ciaran Carson found himself hailed as a standard-bearer for a "Northern Renaissance", a movement centred on Belfast that some have dismissed as a journalistic construction but which, nonetheless, signalled an end to the poetically barren 1940s and 50s.

Edna O'Brien, who has followed Heaney's career from the beginning, "devouring everything he wrote", believes that, once he had emerged from the cocoon of literary Belfast, "his place in Irish literature was guaranteed, secure, and goldplated." "There's a poem in his collection District and Circle [called] The Lift, that is truly great," she says. "His essays, too, are so marvellously luminous, so erudite and accessible." Invited to compare him to Yeats, she demurs blithely. "I'm not going to go down that road," she laughs. "Great writers are unique, and beyond comparisons." From the beginning, then, Heaney always seemed destined for greater things.

Despite his precocious flying start, Heaney says he was still "uncertain at that stage what I was doing". He took a postgraduate year of teacher training, not realising it was a blind alley: "I thought I was going to be a teacher," he says. "The first guy out of the family, and into the trade with a degree."

At this early stage, and throughout his career, Heaney has been susceptible to the influence of stronger artistic talents. Now he met a poet, later a great and enduring friend, who "actually sent a charge of energy through me, a kind of electric Hopkinsian transmission". He had met Ted Hughes.

"I always felt safer for Ted's friendship somehow," he says now, recalling the poet laureate. "He was foundational to me. As you know, he transmitted a desire to be more yourself to yourself." Of their first meeting, he says, almost bride-like, "I recall trembling with excitement and shyness."

The next time they were together, for a reading, Hughes came over with his partner Assia Wevill. "We sat up in my house in Belfast that night after the reading, drinking poteen and singing. Marie sang songs. I think Assia sang some Israeli songs, and Ted sang 'The Brown and Yellow Ale', which he said was [James] Joyce's favourite song. Everybody was young. Assia was quite magnificently beautiful. She said a wonderfully grand and affected thing to me. She could see I was excited and in awe of Ted, and she said 'Poets ought to be like bishops. Each should have his own diocese and meet not all that often, and quite formally.'

I remember Marie had a strong sense that Assia was somehow halted by Sylvia [Plath], and in competition with her."

Now that we're talking about Ted Hughes, a poet who was always so attuned to an unpoliced unconscious, and even the astrological side of creativity, it seems like the right moment to ask about the question of inspiration. Where does poetry come from? In his response to this question, Heaney is probably more pragmatic and Anglo-Saxon than Hughes would have been.

"I think it comes from all the other poetry that's there," he replies. "I think that a relationship with something else is called for - all the other poetry that's around, or the culture, or the times, or your clique - and it calls the poetry out of you." Is there someone who does this? "To get started, what starts you?" he wonders. "You can call it the muse, but it's excitement, the beloved. Certainly, there's a kind of quickening." He begins to describe this excitement. "There is a physical need. I need to feel a purchase on something. I used to say that it was like a bite on the line, or a tug. With me, the purchase is a 'thingyness' or a 'memoryness'". Now he's becoming slightly Delphic, and I sense we're drifting into some ancient Celtic cave.

"It really comes out of - from the side... Like a ball kicked in," he goes on, speaking of this private moment with a tangible, strange reticence. "It's rather risky. I don't keep a notebook. I'm superstitious. I always felt that if I started to be assiduous about it, and looked for it, then it might go away. Or I would turn into a different kind of writer."

So is Marie his muse? "Well, she was a muse, certainly," he replies. I'm not exactly sure what to make of this answer, but before we can go down that avenue, he's switched back to Hughes. "Ted's phrase, which I love quoting, is that the only thing that distinguishes what we call poetry from the other literary arts was that it arrived from 'the place of ultimate suffering and decision' in us." He repeats the phrase with relish and satisfaction, as if it defines something important about his own work.

For Heaney, the Irish Catholic from the North, the central and inescapable fact about his creative life, from Death of a Naturalist (1966) to the present day, is that it had been shadowed, haunted, and occasionally blighted, by the Troubles. If ever there was a place of "ultimate suffering" in Heaney, it must be located somewhere in the historical and psychic trauma of Northern Ireland.

But when you read Heaney's poems, you rarely find any committed parallel narrative. It's as though, from very early on, out of temperament as much as self-preservation, double-agent Heaney chose to step back from, or to the side of, the crisis. To be detached, and uninvolved. To elevate his uncertainty into art, and transmute it into the lyricism of everyday life and the "thingyness" of things. How he executed this manoeuvre is not exactly clear, but there's a story he tells against himself that says a lot about his innate diplomatic skills in navigating the bloody waters of the sectarian North.

When he lived in Belfast during the beginning of the Troubles, Heaney used to buy fish and chips at a shop on the edge of fiercely loyalist territory. One night in the chippy a new assistant, not knowing Heaney as a regular, recognised him from a television arts show the night before. "Oh," she cried, lashing on the salt and vinegar. "I saw you on the box last night, didn't I? Aren't you the Irish poet?"

Before Heaney could answer this, the most loaded of all local questions, the owner of the shop turned from her frying to correct the girl. "Not at all, dear," she said. "He's like the rest of us, a British subject living in Ulster. God," she went on, now speaking directly to Heaney, "wouldn't it sicken you? Having to listen to that? Irish poet!" When he repeats this story, Heaney confesses he was afraid to contradict her. Aren't you the Irish poet? The irony is that, having used all his resources to evade the question, Heaney is now, more than ever, defined in this way.

At this point, Marie Heaney, climbing up the stairs to the poet's "hutch", arrives with cups of coffee. She is recovering from a successful cancer treatment, and wears a wig. Today, she has lost her voice. There's a whispered conversation in which Heaney wonders if it's not too early for "a nip" (of Bushmills), and then we continue.

At first, he says he had been carried along on "a generational conveyor belt". He'd been the "scholarship boy, chosen boy, first class degree. I'd gone into teaching, and had blessedly encountered poetry, the magic of print. I'd been published, and it all just came along. It happened very fast, and I knew that I was being overpraised in my first three books. I wasn't as sure as other people were."

Then, in 1970, he was invited to Berkeley, California, and his eyes were opened. "This gave me a sense that I could make a choice. I wasn't just on the conveyor belt. I could step off it. When we came back from Berkeley in 1971, I was ready to make the move and become a writer, as it were. America influenced me in taking the step to leave Queen's and go freelance."

He doesn't see this as leaving Belfast because of the Troubles, as some have alleged. "I said, I have to verify myself to myself. I would give up the job [at Queen's University]. Among other things, I felt I was drinking too much. The relationship between the move to County Wicklow and the happenings in the North wasn't cause and effect at all, no."

Heaney insists that the cause of his move was what he calls "the writerly desire. It was the right thing at the right tine. But, of course, once I moved there was the sense of historical change, and an editorial in the Irish Times, 'Heaney moves South'. So this was already mythologised, and I couldn't escape the sense that it was a public act as well as a private."

Just before I met Heaney, I had come across a quotation from Thomas Mann's The Magic Mountain, which seemed appropriate. Now I read it out to him for his reaction: "A man lives not only his personal life as an individual but also consciously or unconsciously the life of his epoch and his contemporaries."

Heaney listens thoughtfully, and after a pause, he agrees. "That's true," he says. "You didn't need to be a writer to be living the same life [of the Troubles]. That's what gave everybody who came to the fore in my generation a charge." Temperamentally, he cannot be unambiguous about his answer, and launches into a complicated and not wholly convincing theory about how the poetry of Belfast in the 60s was not related to the violence. But then, having given the diplomatic answer, he concedes that the Troubles had given him "something of consequence" to write about, and that "Something was at stake. I wasn't aware of it at the time, but I'm aware of it since the peace process."

"These were very dangerous times," says Heaney, yielding a point with hindsight. "When the Provisional IRA began their campaign, people like myself, with a strong sense that things needed to be redressed, were excited." Bloody Sunday and its poisoned aftermath polarised everything. Even Heaney lost his cool sufficiently to write a polemical poem, speaking of "My heart besieged by anger, my mind a gap of danger" and of justice waiting to sprout "in Derry where the 13 men lay dead". Looking back to those dark days, he insists that this was a protest poem, commissioned for a rally but never actually performed.

The worst year was 1974. "There was a sense of an utterly wasteful, cancerous stalemate, and that the violence was unproductive. It was villainous, but you were living with it. Only after it stopped did you realise what you had lived with. Day by day, week by week, we lived through this, and didn't fully take in what was going on."

But he always felt it was impossible to take sides, and I ask him if he has ever regretted not being more vocal. "Speaking out," he insists, "one was cornered. My sympathy was not with the IRA, but it wasn't with the Thatcher government, either." He says now that he "didn't want to enter into bigotry," but his deep Irishness was never far below the surface. Again, there's a little episode in his creative life that's more revealing than any commentary.

When, in 1981, Andrew Motion and Blake Morrison placed Heaney in an anthology of contemporary British poetry, he was indignant at being "cornered" and protested in rhyme. "My passport's green", he wrote, "No glass of ours was ever raised/ To toast the Queen".

He now says of this furore that "it was complicated because at the same time I didn't want to pull my books out of Britain. I didn't want to be bigoted. I just wanted clarification, but it was complicated... It was a hell of an uneasy time here, savage. It was an awkward time for anybody who wanted to stand apart from both sides. I didn't want to be too rabid, or enlisted as an IRA spokesperson either.'

He goes on, "As I was living in the Republic, I wanted to call myself Irish. I just felt totally conflicted. I felt I wasn't owning up to something in myself if I ran with that ["contemporary British poetry"]. It's a very ambiguous, uneasy thing, having the British cake and eating it, as it were." Lately, Heaney has become more political, for instance, urging Irish voters to say Yes to the Lisbon Treaty, but the Troubles remain a closed book.

Heaney turned 50 during the murderous final decade of the war in the North. To mark this milestone, he gave himself a year off in County Wicklow, and went to Rome for the first time. Does he go to church? "No. I mean, I go into it. I go to funerals and weddings." He doesn't pray, but "I find myself mantra-ing a bit. I'm not addressing a godhead, but repeating a mantra. But it's like nursery rhymes and belongs in the realms of things known by heart."

During this season of solitary communion with his Irishness, to occupy himself as a fulltime writer, Heaney began some translations from Irish Gaelic literature. He had learned Irish at school. The language was real to him. "If you lived in the Irish countryside as I did in my childhood," he says, "you lived in a primal Gaeltacht." So he translated the Madness of King Sweeney, a classic Irish text. Other commissions followed, notably for Beowulf, a translation which, to his amazement, was awarded the Whitbread prize in 1999. This was part of a prize-winning sequence he shared with his friend and collaborator, Ted Hughes. Several times in our conversation Heaney referred to "Ted" with a deep sense of personal loss.

Hughes died in 1998, three years after Heaney's Nobel Prize. The poet's death was like a great tree falling in the forest; the prize a sudden gale of public exposure: these two events, so unconnected, have combined to leave Heaney isolated, reflective, and facing up to the inevitability of the endgame. A poet who has conducted his life so successfully wants to manage his last years with grace and distinction, and to continue defying expectations.

"Between the stroke and the 70th birthday," he says, "I suddenly realised I had boxed myself into a kind of closing cadence." So now he's doing his best to break out of that box, and says "I'm trying to finish a book of poems to counteract that." He wants to call it Human Chain, another reference to his downstairs exit to the ambulance after the stroke.

There'll be no Yeatsian madness for Seamus Famous. In fact, he takes secret inspiration from one of literature's classic enigmas, confiding that when recently asked by an arts programme which character from fiction he'd like to be, "I said I'd like to be Jeeves."

He is still elucidating the mystery of his life as a poet. "If the truth be told," he says, "it's only now, 14 years later, that I'm realising that I really did win the Nobel Prize. All that time,

I was holding it at bay and diving underneath it, and hurrying through it."

Heaney has reached a moment in his life where he wants to be at peace with himself, and with his society. He quotes, as a kind of epitaph, the messenger's line from his translation of "Oedipus at Colonus": "Wherever that man went, he went gratefully." Here, he catches his own quotation, and laughs. "I'd better watch out that I don't talk myself into a conclusion."

Nothing's easy, but he can find renewal and take comfort in the solitude of his house in Wicklow. He says he still finds it hard to say "No". "I'm haunted by 'ought'," he confesses, conceding that he's probably done too many interviews (including a whole volume of them, Stepping Stones, with Dennis O'Driscoll), and accepted too many honorary degrees. "Again, after the stroke I thought, 'This has got to stop now.'"

Now, more than a decade after the peace process was signed, the lethal, divisive times through which he worked in his prime are part of the Irish past that is always so vivid and present in the everyday lives of the people. "British" and "Irish" have become written into the constitutional settlement inaugurated by the Good Friday Agreement.

The sectarian scars are healing, despite the occasional flaring of violence. Now, says Heaney, "You can have an Irish identity in the North, and also have your Irish passport. As far as I'm concerned, the language has changed, the times have changed, and we have signed up to an open relationship with Sinn Fein." He seems relieved that the ancient Irish blood feud is in abeyance for the moment.

Heaney says he was not involved in the Good Friday Agreement "in any way". But he's known John Hume, its chief architect, for years, and when President Clinton threw himself into the peace process, he recruited Heaney's work to his cause, quoting one of Heaney's most memorable lines "Between hope and history" at every opportunity. The loaded tranquillity of the peace process mirrors the pregnant understatements of Heaney's own poetry.

He will never be drawn into an explicit exploration of his place in this history, or his contribution of "hope", but in answer to his own inner and urgent questions, Heaney knows that poetry must be a private matter. So how does he reconcile the pressures of the Nobel laureateship, and prevent the wind of celebrity from extinguishing the flame of inspiration? "Well," he admits, slightly baffled, "I don't know the answer to that."

The taxi is waiting downstairs. It's time to go into town.

• This article was amended on Tuesday 1 December 2009 because the article referred to Assia Wevill as Ted Hughes's wife but they were not married.