It's 10 years since Bryn Terfel first sang in Mozart's Don Giovanni at Covent Garden. Aged just 26, and three years after winning the runner's-up (officially, Lieder) prize at the 1989 Cardiff Singer of the World, this strapping Welsh sheep-farmer's son was making his Royal Opera House debut as the surly peasant lad Masetto, with just one 90-second solo to his name. As international stardom beckoned, it didn't take Terfel long to work his way up the opera's cast list, via a brief stint as Leporello, the libertine's loyal sidekick. So this month, when he returns to the Garden in Don Giovanni once again, the burly bass-baritone – who two years back donned his bumper belly padding to play Verdi's Fat Knight in the Falstaff that reopened the then refurbished venue – will, of course, be singing the title role.
It's a part he's already played, to great acclaim, in Paris and New York. He'll be singing it again in Chicago soon with the director Peter Stein, in whose famous Welsh National Opera Falstaff he sang Ford to Donald Maxwell's mountainous Sir John. He hopes, however, that he's coming to Francesca Zambello's new Covent Garden staging with an open mind. "I'm always interested to see what productions actually evolve into," he says, with three weeks still to go before opening night, "and this one is shaping up very nicely."
He particularly likes Zambello's use of a "turntable stage" to speed up the scene changes. "We've been watching each other rehearse different scenes, and it's very quick and energetic," he says, "and I think that's the piece." It's also a practical solution to a perennial problem. "Opera houses tend to be warm, comfortable places," he concedes, "and conducive to having a little nap now and then. And there's something about the length of this opera, too. Many times I've sat in an audience and seen whole rows of people, who've paid huge amounts of money for a seat, all fast asleep. So the scenes really have to flow to keep your mind focused on the stage."
As for Giovanni himself, Terfel thinks it's clear from the music that "he's already falling into the depths of the abyss right from the start" (and he hums me a bit of the overture to prove it). Not just falling, either, but failing. "You know, from the moment Leporello sings his Catalogue Aria [that lubriciously voyeuristic number in which the manservant dutifully tallies the totals of his master's conquests country by country, climaxing in the patriotic claim 'Spain: 1,003'] Giovanni never adds to that list. So perhaps he's a Casanova who's fallen on, er..." "Hard times" is obviously not quite the phrase that Terfel (a native Welsh-speaker) is groping for, and he eventually settles, limply, on "things not actually working", before concluding, with a distinctly masculine swell of pride: "He's outlived his virility, you see."
The clue to his characterisation lies in the way Giovanni handles his women: "With brutality. So that's how I play him, as a real Jekyll-and-Hyde psychopath." That said, he accepts it's a role he has to play to his physique. "There's no point in me trying to be a suave, sophisticated Giovanni. I have to make full use of my 6ft4in frame."
It will be interesting to see how the thrust of the production changes when a second cast, headed by the lighter-voiced, leaner-framed Simon Keenlyside (and with Sir Charles Mackerras replacing Sir Colin Davis in the pit), takes over for the last four shows. By coincidence, it was Keenlyside who sang Giovanni to Terfel's Leporello on a 1997 DG recording. Given that master and servant enjoy such a symbiotic relationship in the opera, even swapping clothes at one point, it might have been doubly interesting to have had the two British baritones doing the same, alternating as Don and dupe throughout the run.
As it is, Terfel is delighted to have the American baritone Alan Held as his Leporello: "We're the same height, we can wear each other's coats, we even take the same shoe size. So it helps with that changing of characters in Act 2."
By another coincidence, the role of the Commendatore, the ghostly nemesis who finally drags Giovanni down to Hell, is being sung by fellow (though Essex-born) Welshman Robert Lloyd, a former principal bass with the Royal Opera who once famously recorded a TV version of the "Last Supper" scene in which he played all three male roles: master, servant and "stone guest", too.
"It was a wonderful programme," says Terfel. "I remember seeing it when I was in school." Though not interested in playing such "mind tricks" himself, he admits to being "a bit sad that nobody ever asked me to do what Mozart did originally – that is, sing both the Commendatore and Masetto. It would need an incredibly fast costume-change before the finale, but it would have been interesting to have had a go. But perhaps that'll come when I'm semi-retired and want to earn little pennies here and there."
Oddly, for a young singer at the height of his powers, Terfel is constantly harping on about early retirement from the operatic stage. "I've always said that opera won't be a very important factor in my calendar in forthcoming years. I'm a father of three very energetic boys now, and I do feel they are at an age [seven, three and one years old] when they actually need their father around."
And home, of course, remains the notably opera-free zone of north Wales: "Just outside Caernarvon, that wonderful town with the Edward I castle. Many times I've been up that Eagles' Tower, spitting into the wind!" But one senses, too, a deeper insecurity, a niggling fear that fame might pass as quickly as it came. "I'm singing principal roles, so I'm taking full advantage of my situation, but things can change so swiftly; other singers can run up the ladder much quicker. You know, it always works in leaps and bounds.''
Clearly, he was shaken by the back problems that forced him to bow out of his scheduled Covent Garden debuts as the Flying Dutchman and Scarpia in 2000. Wagner's fateful seafarer, whose tempestuous solo Terfel sang so memorably in his televised bid for Cardiff Singer of the World all those years ago, still seems doomed never to reach home port. "It's always in the plans for the new Cardiff opera house," he says, "and, of course, those plans get shelved every year."
As for Puccini's police chief, he recently tried the role on for size in Amsterdam. It was not, apparently, a comfy fit. "I'm a true believer in fate. They're both peaches of roles, but perhaps somebody was looking after me and trying to tell me it wasn't the time to do them."
If not the Dutchman, though, two other Wagner roles are waiting in the wings. The first is Hans Sachs, whom Terfel will sing on stage in Sydney and then take into the studio to record with Christian Thielemann. But the really big news for British Wagnerites is that Terfel will be singing his first Wotan in the new Covent Garden Ring, to be directed by Keith Warner in 2005. That's the year Terfel turns 40, but he insists this is a coincidence. "I just think it's a particularly good time to take over certain realms. Certain Wotans have been singing for quite a while now" – naming no names – "so it's 'in with the new', I guess."
He can't pretend that playing top god has always been one of his burning ambitions. In fact, despite winning the Royal Opera's Wagner Bursary as a student, he's always rather avoided the composer for fear of being type-cast. "I'm all about feathering my cap in different careers, you know, and in different styles of music."
What really seems to have persuaded him to take on the Ring is Tony Pappano's imminent arrival as the Royal Opera's new MD. "He's a man I love working with. I love his energy, the way he always keeps in touch: he rings you, he e-mails you, he just checks up on you. Whereas when I cancelled the Dutchman here, and I was in all this pain after my operation, I didn't receive one letter even to see how I was. You need the personal touch in institutions like this." Meanwhile, he's just sung Dulcamara, the quack doctor in Donizetti's Elixir of Love , in Amsterdam: "The director had me play him as a kind of Elvis crossed with Liberace. I came on surrounded by ballet dancers, all topless – I could barely remember my words!"
Hopefully, that won't be a problem this Sunday, when he gives a recital at the Barbican. Alongside songs by Schubert, Copland, Vaughan Williams and Quilter, he'll also be giving the UK premiere of a new song-cycle, The Moon is a Mirror, written for him by Jake Heggie, the 40-year-old resident composer with San Francisco Opera. Heggie enjoyed a huge hit with his debut opera, Dead Man Walking, a couple of years back, and his accessible, singable style seems to have made him the composer of choice among the US's leading recitalists – women especially, with the likes of Renée Fleming, Sylvia McNair and Jennifer Larmore all queuing up to sing on his debut CD.
Frederica von Stade is a particular fan; it was she who recommended Heggie to Terfel when Credit Suisse offered to commission a new work for him to take on an Asian tour. "I wanted something fairy tale," recalls Terfel, "something that my children would react to or that would perhaps bring out the child in me. Jake instantly suggested these poems by Vachel Lindsay, all about what particular personalities – a snowman, a miner, a monk – think of the moon. I also told him: I want something tuneful, I don't want anything 'modern', give me something that an audience will react to – because, in the end, we're the ones that have to stand there and sing these pieces. And he took it all on board. The three songs he wrote are fantastic. I really enjoyed performing them."
So much so that he commissioned two more himself. "I asked him to give me a couple of real showman songs that I could use as a calling card in a way. So the one that ends the cycle is a top-hat-and-tails kind of a character. That's what my evening of song is. I don't need intellect to be a barrier for music. I just want to have fun."
Recital, Barbican, London EC2 (020-7638 8891) 7.30pm tomorrow; broadcast, 7.30pm Monday, Radio 3; 'Don Giovanni', Royal Opera House, London WC2 (020-7304 4000), opens 22 January