No conductor has a more extraordinary story to tell than Mariss Jansons. Thirteen years ago, while conducting La Bohème, he had a heart attack. He slumped to the floor, but his hands continued to conduct the music. Those hands, determined to keep faith with Puccini, were all that the audience and orchestra could see as Jansons fought for his life.
A call went out: "Is there a doctor in the house?" A third of the audience rushed forward. Researchers who wish to discover how middle class a classical music audience is need look no further than that evening.
Jansons survived that heart attack and another one five weeks later, and now, a decade on with a defibrillator inserted into his heart, the Latvian who runs two orchestras – the Concertgebouw in Amsterdam and the Bavarian Radio Symphony Orchestra in Munich – he stands at the peak of his profession. Sir Simon Rattle has proclaimed him the greatest living conductor. And Gramophone magazine's list of the world's top 10 orchestras has Jansons' two outfits at numbers one and six respectively. It is a phenomenal achievement.
Today, Roger Wright, director of the Proms, will announce as one of the season's highlights that Jansons is coming to the Proms this year with his Amsterdam orchestra. Wright and the Proms will be getting a maestro who quickens the pulse. But they will also be getting one who is unashamedly outspoken, who has, behind his friendly demeanour and impish smile, the most forthright views, as I discovered when I met him at the Lucerne festival last weekend.
Watching him there perform Tchaikovsky's fourth symphony with the Bavarian Radio Symphony Orchestra was an unforgettable experience. On the rostrum, Jansons seems nothing like a man who should be concerned about the state of his heart. He fixes the musicians with his eyes, body seemingly poised to dart, like a greyhound in the traps. At the start of the symphony as the horns reach a sudden climax, he bounds forward with such a sudden movement that you think he will crash into the violins. A few minutes later his face is lost in such rhapsodic intensity that you fear he might forget to wave the baton again. But soon he is almost dancing on the spot, his shoulders moving up and down, his frame twisting one way and another, his hands making wide, expansive arcs, and the look of rapt intensity replaced by that impish and encouraging grin. At the last bar of the symphony he jumped on the rostrum.
Chatting back at his hotel, he told me that he loved coming to the Proms – "The Royal Albert Hall is special and the Proms are unique," he says. "There's a unique atmosphere, so you excuse everything. You excuse the sound. The enthusiasm of the people, especially the young people, is wonderful."
You excuse everything. Yes, Jansons has a point to make, as always. It is that in London there is a lot to excuse. Everyone knows that the Royal Albert Hall does not have great acoustics. But the Barbican and the Royal Festival Hall, after its multi-million pound refit, have fed us with propaganda that they have terrific acoustics and are world-class concert halls. The world's greatest living conductor begs to differ.
"I must be honest with you," he says. "The Barbican and Royal Festival Hall, they are not very good halls. The very good halls in the world are few." He reels off a list including Berlin, Vienna, New York, Los Angeles, Lucerne. He does not mention a British city.
"The Royal Festival Hall is too big. It seats over 2,000. If a hall is too big it is less likely to sell out and it is not good for the acoustic."
Concert halls are Jansons' obsession at the moment, as he is trying to get a £100m hall built in Munich for his orchestra. He is not exactly short of influential admirers – the German Chancellor, Angela Merkel, came to his New Year concert – but he is upset that no guarantees have been given to him, not least when the city's operas and a rival orchestra have their homes.
"We are in a very terrible situation. I have to rent a hall, and this is one of the best orchestras in the world. I could not expect this somewhere like Germany. My dream is to have a hall with a fantastic acoustic, and the acoustician and architect should not fight over who is the more important."
Germany is not the only country that can cause Jansons occasional depression. When I mention his homeland, or perhaps less precisely the former Soviet bloc, present day Russia and attitudes to music and culture, he darkens. "I'm very depressed about it, that the spiritual part, the cultural side is going down... This was the strongest side of our country, education was fantastic.. Now good teachers go abroad, the quality of music is not good. There's this strong striving to get money. And I must tell you that money everywhere in the world delays the spiritual part of the human being. It's not only Russia. Everywhere there is a big problem. The people with money are not taking care of spiritual development."
On a happier note, we talk of the consensus that his orchestras are now among the world's very best. I ask him what makes an orchestra great. "Great players, certainly. And then an enormous drive to get to the right level; proud to show high quality; and I think individuality and musical intelligence, which means that you can speak with musicians on a high level about your interpretations, and not just work on the primitive level. They must have a drive that never allows them to play below their level."
And a conductor? What makes a conductor great? "Talent. Good technique. There must be profound, fantasy-full interpretations, and great interpretations in the concert, and ability to feel the style of music and to have good rehearsal technique and wide repertoire."
For Jansons, now 65, conducting is in the blood. His late father was head of the Riga State Opera. It was he who suggested Mariss to the Oslo Philharmonic, an orchestra that Mariss took to world fame. As a young man, he was spotted by Herbert von Karajan, who invited him to work with the Berlin Philharmonic, but the Soviet authorities, fearful of another defection, forbade it, and he became assistant music director of the Leningrad Philharmonic. His home is still in the city, now, of course, St Petersburg. He used to drive between there and Oslo, in the early days packing his car with food as he couldn't afford Western prices.
Remembering the night of his heart attack, he tells me: "It was terrible, really terrible," adding, curiously, "it was very exciting. I like enormously this opera. I conducted and everything went fantastically and seven minutes before the end I suddenly felt terrible pains in my left arm and heart and I knew immediately it was very serious. The question was what to do now. I must save my emotional energy. So I decided I will do very small movements. Stopping was not an option. I felt worse and worse. I had no strength and it was completely dark in my eyes and I said to the orchestra leader I feel very badly. Then I don't remember anything. The musicians told me afterwards that I still conducted."
Stopping still isn't an option. Now he has a passion to take on a world, which, according to him, is turning his back on culture. And to make London's concert hall managers sit up, listen and realise that they need to get their acts together.
Mariss Jansons and the Concertgebouw Orchestra perform two Proms this season, on 1 and 2 September ( bbc.co.uk/proms ) and appear at the Lucerne Festival on 3 and 4 September ( www.lucernefestival.ch )