In Germany, the Classical tradition lives on, so that even popular newspapers will call some political veteran “the Nestor of his party”, and it is commonplace to refer to the Wagner family as “the House of Atreus”, after that other clan whose internecine hatreds and gruesome fate are lurid even by the standards of Greek mythology. So when Gudrun Mack married Wolfgang Wagner in 1976, she plunged into the middle of a bickering clan whose quarrels have only intensified since, and not least because of her.

She was born Gudrun Armann in Allenstein in East Prussia, as it still was, though not for much longer. Shortly after her birth, her mother fled in the face of the advancing Red Army, taking her daughter to Bavaria, where she grew up. Young Gudrun trained as a linguist and secretary, and in 1965 replied to a job advertised discreetly by a “cultural institution in northern Bavaria”, which turned out to be the Bayreuth Festival.

Founded by Richard Wagner to stage his own operas, the festival was run in succession after his death in 1883 by his terrifying widow, Cosima, their son Siegfried, and then, after those two both died in 1930, by Siegfried's widow Winifred, frightful in a different way. She made Bayreuth an official temple of the Third Reich, where she entertained her friend “Wolf” — Adolf Hitler.

Siegfried and Winifred had two sons, Wieland and Wolfgang, as well as two daughters. Despite their and their mother's dubious conduct during the war, the brothers relaunched Bayreuth in 1951, to celebrate the supposedly progressive and democratic Wagner, a project which looked even less convincing when, many years later, Winifred emerged from the shadows to express her undimmed love for “Wolf”.

When Gudrun arrived to join the Bayreuth press office, Wieland was still alive, having transformed the style of Wagner production, and also caused much scandal in his private life. But he died the following year, in 1966, not yet 50, leaving the festival in the hands of Wolfgang, who directed numerous operas himself, albeit to little critical applause. In 1970 Gudrun married the festival dramaturge, Dietrich Mack. She then moved offices to work as Wolfgang's personal assistant.

He had been married for more than 30 years to Ellen Drexel, the mother of his daughter Eva and son Gottfried, but Wolfgang and Gudrun married after divorcing their respective spouses, and their daughter Katharina was born in 1978. Thereafter, while Gudrun displayed a considerable talent for organisation in the administration of Bayreuth, Wolfgang ran the festival and devoted his energies to securing the succession for his second family: he was estranged from Eva and Gottfried, and also wanted to exclude Wieland's children.

At first Gudrun herself appeared to be the anointed successor, not least in her own eyes: “I am my husband,” she once told a telephone caller who asked to speak to Wolfgang. But as the years went by, as Wolfgang remained immovably at the helm, and as Gudrun herself approached the normal age for retirement, they turned to their daughter. Indeed, in the view of the critic Wolf-Dieter Peter, speaking on Deutschlandradio on the day of Gudrun's death, Katharina had been hand-reared by her mother from the beginning to take over.

Recently Katharina proposed a triumvirate to run the festival: Peter Ruzicka, sometime director of the Salzburg festival, the conductor Christian Thielemann and herself. This summer, still only 29, she staged Die Meistersinger. It was her first production at Bayreuth, and by way of her job application, but the barrage of critical derision scarcely furthered her cause. She will not succeed without competition from her half-sister Eva Wagner-Pasquier, who has worked at the Royal Opera in London and now the Met in New York, and her cousin Nike Wagner, Wieland's daughter, who would like to run Bayreuth together. A resolution of the matter is urgent, since Wolfgang — the grandson of a man born in 1813 — is now 88.

Gudrun's untimely death was quite unexpected, and came a day after she had undergone routine surgery, apparently without ill-effect. With a touch of hyperbole appropriate for the occasion, Günther Beckstein, the state governor of Bavaria, said that “she shaped the lustre and the worldwide significance of the Wagner festival”. Whether or not that is entirely true, her death must hurry a decision.

Gudrun Wagner is survived by her husband, Wolfgang, their daughter and the two children from her first marriage.

Gudrun Wagner, Bayreuth administrator, was born on June, 15, 1944. She died on November 28, 2007, aged 63