And there is also the fact that, like Domingo, Kaufmann is an excellent, instinctive actor. ‘He brings a protean talent in that he can shift and change,’ Jonathan Kent points out. ‘For instance we were rehearsing a very difficult scene [in Manon Lescaut] at the end of Act II where the two lovers know they are about to be trapped… I’d ask the performers to do the chaos of panic, with people running round not knowing how to escape. Jonas brings endless invention to that and he can do it while singing. He can think on his feet. He can throw himself around the room and still hit the notes.’  Kaufmann is 20 minutes late for the section of rehearsal I have been invited to, which leaves only another 20 before the lunch break. He apologises gaily, and no one murmurs. It is a modern production (designed by Paul Brown) and the death scene is taking place on a broken flyover, a vast piece of stage machinery currently inhabiting one of the opera house’s even more vast rehearsal spaces. Kaufmann shins up the ladder of the set, wobbling it for fun as he goes, and pulls a face when he gets to the top. Then he takes the soprano Kristine Opolais in his arms and gets serious.  As he and Opolais practise various positions of collapse while singing the opera’s closing moments, he is two people, shaking with laughter one moment, then racked with wholly convincing torment the next. And he is dominant: directing as much as Kent does. ‘Are you singing my line?’ Opolais says at one point. ‘You’d better be quick or he’ll sing the whole act,’ Kent says, laughing.  This is a tenor with the world at his feet, perhaps a little cocky, but not at all lofty. ‘I really got lucky, in a million ways I got lucky,’ is how he describes it when we meet at the end of the rehearsal, five hours later. Sitting in a rather more cramped corner of the opera house’s backstage area, initially I have the sense of an overgrown boy opposite me; a feeling exacerbated by the length of his Byronic curls – despite the greying at the temples – and his outfit of a casual grey T-shirt and jeans. He is about 5ft 11in and slim. His speaking voice is deep and loud, as if he is permanently projecting.  As Don Jose in Carmen at the ROH in 2006. PHOTO: Redferns/Getty  Kaufmann was born in Munich in July 1969 to an insurance broker and a kindergarten teacher who were East German by origin. His parents’ families had fled their respective parts of the German Democratic Republic in the early 1960s. They would visit their relations in East Germany when Jonas and his elder sister, now a teacher, were children. ‘[My relations] thought each second the Stasi would smash down the door and come in,’ he remembers.  His family rented an apartment in a block in the Bogenhausen district of Munich that was constructed expressly to help cope with the influx of East Germans. It was here that he grew up. His paternal grandfather, a banker and devoted Wagner fan, lived in another flat in the same block.  Kaufmann describes their lives as ‘conventional’, but the family had an exceptional passion for classical music. ‘All my family members played the piano,’ he remembers. ‘There was always a piano in the room. My parents had subscriptions to everything available. Concert series, opera, theatre. They took us too. We got used to that.’  The first opera Kaufmann saw was Puccini’s Madame Butterfly, aged seven. ‘I thought it was real,’ he says. ‘I was destroyed when [Butterfly] came out for the curtain calls and she wasn’t dead any more.’  He says he was – like all the other children – sitting next to the radio every Friday afternoon to record his favourite songs from the pop charts as well. But it was classical music that was his ‘normal’. He started singing in choirs as a child – at first because his hands were too small for the piano. He continued after his voice broke, and remembers facing down the derision of his schoolmates as he did so. ‘I was 17 or something, and we did a concert and I sang some arias. The whole room started laughing and giggling. They had never heard anything like it before,’ he says.  Despite his talent for singing, Kaufmann says, ‘I never thought I was something special. I never thought about music as my profession, it was just great fun.’ And so, following the advice of his father to make plans for a serious profession with a secure income, he enrolled as a maths student at the University of Munich after secondary school. Realising this wasn’t where his passion lay, he rebelled and switched after two terms to study to be a singer at Munich’s Academy of Music and Theatre.  Years performing in the smaller German opera houses followed; he graduated to the larger European ones by his late 20s. He got his major international break when he sang opposite the most in-demand soprano of the day, Angela Gheorghiu, in Verdi’s La Traviata at the Met in 2006. The world-class engagements have come along steadily ever since.  As a result of his popularity with opera houses and festival organisers, his life is now frenetic. In the next six months, until the end of the year, Kaufmann’s schedule will take him to 11 countries, from Europe to Japan, America and Australia. He will return to Munich, which remains his home, three times for work. This has been the pattern of his life, with minor variations, for about the past 10 years. It is like being a pop star on permanent tour.  Opposite Angela Gheorghui in his breakthrough role in Verdi's La Traviata at the Met in 2006. PHOTO: AP  He gets to Munich when he can. ‘I do a new production there each year and also one revival, which is a total of about eight weeks plus some time off, like a weekend, when I would go back,’ he says. ‘The maximum I would be back home would be 20 to 25 per cent [of the year].’  He says his peripatetic existence means he is too busy to take exercise. ‘Keep fit? I sing!’ he says. (Though he does do some yoga.) And as for his downtime… ‘What downtime? What are you talking about?’ He laughs heartily. ‘Yes, I go skiing,’ he admits. ‘I go sailing, I go hiking, but for very short periods in the year. More to relax, and not to stay fit and healthy. Maybe a couple of weeks a year. This summer I will have three straight weeks off, which is great, I haven’t had that in years. There are usually about 10 days during the year and that’s it.’  It is a life of total focus and absorption, that extends to such details as drinking salt water during performances to put off the threat of low blood pressure, which can cause dizziness. It comes too with an arguably valid anxiety about health (he had a lymph node removed in 2011) that has given him something of a reputation for cancellations.  In Parsifal at the Metropolitan Opera House in New York in 2013. PHOTO: AP  That is one reason why he bucks hard against the pressure opera houses now put on their stars to sign up to shows taking place in five years’ time. Another is that he can’t know what parts his voice, which is developing all the time, will be ready for that far ahead. ‘I can’t find enough singers to go on strike to say we’re not going to sign anything over two years. But it has become insane, I think. The thing to do is to say no to almost everything and there will still be something that comes up at the last minute.’  I ask Kaufmann who his second pair of ears is, the person he turns to for frank criticism. ‘I have some friends, I have some coaches, I have a wife who is a singer too, you know,’ he answers. The catch with this is that he announced the end of his marriage to the mezzo-soprano Margarete Joswig on his website in April. Their union had lasted the better part of two decades, the pair having met at the opera house at Saarbrücken at the start of their careers; and they have three children together of eight, 11 and 15.  The split, it seems, is a casualty of his career. ‘We have agreed it doesn’t make any sense to tell anything about it,’ he says now. ‘But I’ve talked about the circumstances actually. I’m not the only one sitting in that boat. All musicians who do this kind of job have this struggle to combine private life and work. I’ve been pointing that out in almost every interview. That’s the way it is.’  With Anja Harteros in Don Carlo at the Royal Opera House in 2013. PHOTO: Alistair Muir  Yet, of course, Kaufmann loves opera, despite its constraints. He quotes Herbert von Karajan’s description of the experience of performing classical music as an exercise in ‘controlled ecstasy’. ‘When you are performing you should forget about everything around you,’ he says. ‘You should forget that you are a singer, that you are on stage. You must think that your colleagues are real people… and that there isn’t an audience attending. You can come to a point that you can do it so convincingly that you believe it is you who is saying this, you who is suffering.  ‘I think it’s great [to perform like this] but not every musician has it, and not every musician is seeking it, actually. There are musicians who are brain-guided; they seek perfection, not passion.’  With this our conversation comes to a close, and Kaufmann bounds up out of his chair at the realisation that a friend of his is at a nearby pub and is keen to see him. As he leaves, the press officer shows him an advertising board for the new season which shows a grainy close-up of Kaufmann and the soprano Anna Netrebko in an embrace. It must be about 5ft high. ‘Oh I love that,’ Kaufmann says (he’d like a copy). ‘See,’ he gestures to me. ‘The passion!’  To read more from the Saturday Telegraph magazine visit telegraph.co.uk/magazine
He is fluent in four languages, with an unparalleled vocal range and the   instincts of an actor. Meet opera superstar Jonas Kaufmann