As he awaits the British reviews of his translation of The Divine Comedy, Clive James talks to Robert McCrum about his illness, his marital split, TV criticism and his 'joking seriousness'

"I'm told that I'm looking quite shiny," says Clive James, putting his best face on things with a vintage display of Anglo-Australian stoicism. It's an instinctive optimism that is what you'd expect, but still it is moving.

Almost everything in the life of this great literary polymath is edged with darkness. James now dwells in a kind of internal exile: from family, from good health and from convivial literary association, even from his own native land. His circumstances in old age – James is 73 – evoke a fate that Dante might plausibly have inflicted on a junior member of the damned in one of the less exacting circles of hell.

James's health has lately been so bad that, last year, he was obliged publicly to deny a viral rumour of his imminent demise. Two or three times, indeed, since falling ill on New Year's day in 2010, he has nearly died, but has somehow contrived (so far) to play the Comeback Kid. Perhaps he has found rejuvenation in the macabre satisfaction of reading premature rave obituaries from fans around the English-speaking world. If word of his death has been exaggerated, there's no question, on meeting him, that he's into injury time, with a nagging cough that punctuates our conversation.

"Essentially," he says, as we settle into the rather spartan living room of his two-up, two-down terraced house in Cambridge, "I've got the lot. Leukaemia is lurking, but it's in remission. The thing that rips up my chest is the emphysema. Plus I've got all kinds of little carcinomas." He points to the place on his right ear where a predatory oncologist has recently removed a threatening growth. "I'd love to see Australia again," he reflects. "But I can't go further than three weeks away from Addenbrooke's hospital, so that means I'm here in Cambridge."

In a recent, valedictory poem, "Holding Court", which describes his involuntary sequestration, he writes: "My wristband feels too loose around my wrist." In all other respects, he is tightly shackled to his fate.

Exiled from his homeland, where he has now become a much-loved grand old man of Australian letters, James is also exiled in Cambridge. His wife of 45 years, the Dante scholar Prue Shaw, kicked him out of the marital home last year on the disclosure of his long affair with a former model, Leanne Edelsten. This betrayal also devastated his two daughters, though it has ultimately brought them closer to their father. In "Holding Court", James writes ruefully that "retreating from the world, all I can do, is build a new world".

He is doing that this month in the only way he knows, and in the way he has always done – in print. With a grim appropriateness, his new book is an extraordinary verse-rendering – the fruit of many years' work – of Dante's The Divine Comedy. According to TS Eliot, this is the only book in the western tradition that surpasses Shakespeare. It is typical of James's chutzpah that he has not only tackled this Everest of translation, but has scrambled to the summit in triumph.

James reports that, in Australia, he has been getting "wonderful reviews, which is very gratifying". Now, he waits with some apprehension for the British critical response, knowing all too well that over the years he has been acclaimed as an entertainer but mercilessly criticised as the clown who wants to play Hamlet.

Flak is something he has had to deal with from the minute he decided to leave Kogarah, New South Wales. James comes from that remarkable generation of ambitious postwar Australians – other members are Robert Hughes and Germaine Greer – who felt they had to get out. "We all thought that the real action was overseas," he says. Any regrets about not going back? He has been burned too often by the Sydney media to answer that easily. "Let's just say, yes – and no," he replies. "Australia offers a wonderful life, but I've made my life here." Tellingly, he slips into the past tense to consider his career. "I didn't get a bad ride. I managed to square the circle."

Vivian Leopold James (he adopted "Clive" after Vivien Leigh as Scarlett O'Hara made his name seem girlish), born in 1939, has said that "the other big event of that year was the outbreak of the second world war". Challenged with this now, he laughs and says: "Dramatising myself is what I do." A prisoner of his childhood, as he puts it, he landed in England in the winter of 1962, having promised his Sydney friends he would be gone for just five years.

But then he went to university in Cambridge. James, slightly older than his fellow students, became a leader of the revels and discovered a taste for mixing erudition with performance. He has been showing off ever since.

Could he have become an academic? "I would have been a bad don," he admits. "I was always haring off to London. I would not have been sufficiently interested in my students – that's a character weakness. I'm not humble enough, and the capacity for ordinary work is not in me. The necessary sense of duty to my students would have been missing."

In place of the ivory tower, James gravitated to the pub, the celebrated Pillars of Hercules – centre of the 1970s Grub Street of Ian Hamilton, Karl Miller and Terry Kilmartin. After some false starts, he landed the job of TV critic for the Observer that would shape his career. "Terry Kilmartin, then Observer arts editor, was the key to it," he remembers. "I used the column to analyse British culture, writing about everything."

Presenting Clive James on Television on ITV in 1987. Photograph: ITV/Rex Features

And, of course, to entertain. Clive James on television became a weekly must-read, importing an Aussie irreverence to rival that of Barry Humphries as Dame Edna Everage. The best of his observations – for instance, that "Perry Como gave his usual impersonation of a man who has simultaneously been told to say 'Cheese' and shot in the back by a poisoned arrow" – had an unequalled, surreal hilarity.

Never mind the influence, feel the power. Charlie Brooker, writing in the Guardian, noted that James "has a way of gliding through sentences, effortlessly ironing a series of complex points in a single easily navigable line, before leading you face-first into an unexpected punchline that makes your brain yelp with delight." James, in his prime, could nail any subject with a single phrase. Famously, he compared Arnold Schwarzenegger in Pumping Iron to "a brown condom filled with walnuts".

Behind the laughter, James hankered after seriousness, plugging away like Sisyphus at poetry and critical essays, and later some fiction. "I still suffer from a blurred image", he says, "but I don't mind." (I suspect he does.) Defensively, he celebrates the great Italian poet Eugenio Montale's approval of "a joking seriousness". Repeating the phrase in Italian for emphasis, he adds: "The Americans especially don't like humour mixed up with seriousness."

So what is he? At the front of his Dante translation, the list of his works is arranged in an imposing menu of fiction, verse, criticism, travel and autobiography. Is he "a man of letters?" James demurs: "No, no – that's too pompous, and so is 'poet'. I would say that 'writer' is still the best." What about writer-performer? "There you go again," he counters, "blurring the image."

James's five volumes of autobiography have all been bestsellers. He has admitted that much of what he wrote in the early volumes about his unpromising origins are "a palpable fantasy". But the central character was recognisably James's true, imperfect self. He was pulling the classic stunt of sending himself up in the spirit of shameless self-promotion. Who else could get away with comparing himself to Byron? In Unreliable Memoirs, and the volumes that followed, James managed to make much of a confession that he was conceited and pretentious, all the while being entertainingly both.

Making mischief has never ceased to excite his imagination. In the 1970s, having made friends with the literary musketeers of the New Statesman (Martin Amis, Christopher Hitchens, Ian McEwan and Julian Barnes), he claims he floated the idea of re-animating what FR Leavis loved to denounce as the "modish London literary world", and suggested that this metropolitan cabal met for lunch. "In retrospect," he explains with relish, "it looks like a conspiracy, and the fun at the time was to make it seem like a conspiracy. But it really wasn't. It was just lunch." The lunching Clive James was renowned for flashing plenty of literary skirt – references to the Russians, allusions to Mandarin poetry, and a touchingly sincere auto-didacticism. The rumours of his legendary self-improvement linger. Tom Stoppard's comment on the news of the Dante translation was to be "faintly surprised he's not trying to translate something from the Chinese or the Hungarian".

When, in 1982, he left Fleet Street to go into TV – another chapter of accidents, reported in a volume of memoir entitled The Blaze of Obscurity – he seemed wilfully to compromise any claim to a serious literary reputation. He admits as much, conceding that only "after a quarter of a century" has his reputation begun to recover from his life in the crystal bucket. TV – Clive James on Television, Saturday Night Clive – pitched him into the company of starlets, minor European royalty and, he tells me, "a number of people who are now in jail". There were some encounters – such as his strange passion for Diana, Princess of Wales – that now read like episodes from Inferno.

Dante is a first love, and one that is further braided into an old love through Prue Shaw's lifelong study of medieval Italian poetry. If The Divine Comedy is, finally, a 500-page meditation on love's ceaseless dramas, then James's translation derives its inspiration from his own nearly 50-year association with a great Italian scholar.

In the introduction to his translation, which is really a love letter to his estranged wife, James recalls the first time, long ago in Florence, that she explained to him the complex subtlety of the Paolo and Francesca episode in canto 5 of Inferno. "Though it was assembled from minutely wrought effects," he writes, "the episode really did have rhythmic sweep. Every moment danced and the dance was always moving forward."

As a contestant on University Challenge in 1968. Photograph: Granada North 0161 827 2497

Whenever the younger James played truant from his Cambridge studies to look at one of the many, often hardgoing, translations of Dante, he convinced himself that "the job was thankless". Instead, for 40 years he threw himself into London's human comedy, diverting himself with a myriad literary and televisual distractions, dazzled a generation, had more than his 15 minutes of fame, then retired.

He returned to The Divine Comedy shortly after 9/11, during a holiday in Greece. All at once "I thought I could see how a translation might work," he says. Rather than attempt to render the notoriously difficult music of Dante's terza rima into English ("That's a killer"), he would adopt a more familiar poetic narrative strategy, one that was almost as familiar to him as breathing, and translate the 14,000 lines of The Divine Comedy into quatrains.

The result, just published, is a revelation. The reader is swept up in the drama of Inferno, which James describes as "the action movie, a PlayStation game". He has taken quite a few liberties with the text – which will not please Dante scholars – but only to put rocket fuel into a vintage motor. He has managed to find the right contemporary tone to express the glittering serenity of Paradiso. The tempo and texture of the poem has an inevitable majesty, but there is also a dancing levity that is suited to James and his "joking seriousness".

He's certainly given it all he's got. The project has been more than a decade in the making. "After I got ill," he says, "I was keen to live long enough to see the book published." The translation has another therapeutic function: to restore his marriage. His wife, he says, has been a great enthusiast for his efforts. So are they reconciled? "That's putting it a bit high," he replies. "It's something I would dearly wish, but it may not be in the realm of the possible. All I can say is that we have been known to break bread together."

For the moment, he is basking in the pre-review attention, planning a sixth volume of memoirs, provisionally entitled Prelude to the Aftermath, and shaking his head over the horrors of the latest Dan Brown, another rival – of sorts – in the Dante stakes.

I wonder, towards the end of our conversation, if the Italian master has taught him any lessons about how to live. "Don't get exiled," he replies, with a final roar of laughter.

• The Divine Comedy by Dante, translated by Clive James, is published by Liveright