Knight at the opera finally takes centre stage with his Czech mate

Playing the lead is Sir Simon Rattle, Britain’s finest conductor, blessed with genius and fted as a hero in concert halls from Berlin to Birmingham. His love interest is the glamorous Czech-born diva Magdalena Kozena, praised for her "impeccable" soprano, photographed by Vogue and the star of this year’s Proms.

Despite being 18 years his junior, Miss Kozena falls for the maestro. A love affair ensues, they leave their spouses and start a new life together.

But this is not a stage production - it is a real-life love story that has sent a frisson of excitement through the gossipy world of classical music.

Last night, to end the speculation, the couple released a joint statement via Sir Simon’s spokesman. It read: "Sir Simon Rattle and Magdalena Kozena have confirmed that they are indeed a couple and living together. All the relevant parties concerned are fully conversant with this situation. There will be no further comment."

It is an unlikely match.

Miss Kozena is blonde, beautiful and 30. Sir Simon is approaching 50 and, although musically gifted, is not noted for his ravishing good looks.

More importantly, both are married - Miss Kozena to the French baritone Vincent le Texier; Sir Simon to his second wife, the writer and former Hollywood film director Candace Allen.

The couple’s friendship began last summer amid the magical setting of Glyndebourne. Sir Simon was directing Miss Kozena in Mozart’s Idomeneo, in which she was widely praised by critics for her voice and looks.

The pair struck up an instant rapport. In an interview at the time, Miss Kozena described working with Sir Simon as a "dream".

She said: "He knows about Mozartian style, but he’s not stuck in ideas from a book. He brings fresh things that may have nothing to do with period, but they’re alive. Working with someone like this is heaven."

On Wednesday night, Miss Kozena was the star singer at a BBC Proms concert highlighting the musical links between Mozart and Prague.

Sir Simon is due to perform at the Proms once next month and twice in September.

Tickets for performances by the pair of Mozart and Haydn works, scheduled in London and across Europe over the next 12 months, are now likely to sell even faster.

Sir Simon has enjoyed a glittering career since he first came to prominence after joining the City of Birmingham Symphony Orchestra as principal conductor at the age of 24. He later became its music director and transformed CBSO’s fortunes over 18 years.

In 2002, he became chief conductor and artistic director of the Berlin Philharmonic.

Critics say that part of the freshness of Sir Simon’s approach, and his broad musical sweep, is down to his unusual musical education.

Instead of beginning with the classics and moving on to modern works, Sir Simon developed a love of 20th-century music at school. His first Beethoven symphony recording did not appear until 2002. His gift has been to bring a crisp, imaginative interpretation to his music.

But the man who is uncomfortable being called Sir has had an interesting private life since living through an earthquake in Pasadena in 1994.

Deciding that life was too short, in 1995 he divorced his wife of 15 years, Elise Ross, an American singer with whom he had two sons.

He married Candace Allen, who remained in their Islington home while he continued to work from Berlin.

But last night it emerged the couple had separated after eight years.

Ms Allen’s father, Dr Edward Allen, was reported as saying: "My daughter told me that Simon has left her for Magdalena. She is distressed."

Sir Simon, who recently admitted, "I see the hall more than I see my wife," has suffered professionally in recent months.

In April, a German critic accused him of "uninspiring", "insipid" and "insubstantial" music-making.

Illicit affairs and classical music are no strangers. Last year, a passionate affair was exposed between Leonard Slatkin, conductor of the BBC Symphony Orchestra, and the percussionist Evelyn Glennie, after her husband found a string of revealing e-mails on her laptop.

Andr Previn, the septuagenarian Oscar-winning conductor, married his fifth wife - a German violinist 33 years his junior - two years ago, while Jonathan Dimbleby's friendship with the late opera singer Susan Chilcott is said to have precipitated the end of his marriage earlier this year.