The legend of Tristan and Isolde (also known in some versions as Iseult) dates back at least to the Middle Ages. Tristan is depicted elsewhere as one of King Arthur's Round Table Knights but in this story acts as an emissary of King Mark of Cornwall, charged with bringing back Isolde from Ireland to be Mark's bride. By accident or trickery, however, Tristan and Isolde share a love potion, which rather interferes with the plan and sets the scene for an epic battle between love and loyalty. With pride, revenge, sorcery and romance thrown in, this is the perfect fare for Richard Wagner, whose glorious music matches the grandiose plot.

It took me many years to appreciate Wagner's opera I had tried listening to them, but did not see what all the fuss was about. Then I saw his Ring Cycle and I began to understand. Other composers wrote glorious music, with every aria warmly applauded, but Wagner was different. His music was seamless, giving the audience no chance to applaud and interrupt the narrative. His music told the story as much as the actions did and swept the audience along irresistibly. This is never more clear than in Tristan and Isolde, with its celebrated "Tristan chord" introduced in the second bar of the overture. Not so much a chord as a discord, it introduces a tension in the music that matches the conflict in the plot. The dissonance demands resolution, but Wagner takes four hours to reach it, toying with our patience until a glorious harmony is finally achieved at the end.

With great demands placed by the composer on both the orchestra and the singers, all the performers are stretched to the utmost and the Glyndebourne cast were fully up to the task. As Tristan, Australian tenor Stuart Skelton has the powerful voice needed for Wagnerian opera and he was vocally well matched by Finnish soprano Miina Liisa Värelä as Isolde, though both seemed a little cumbersome in their movements around the stage.

Glyndebourne coped well with the problems caused by an accident to Scottish mezzo-soprano Karen Cargill in the role of Isolde's maidservant Brangäne which left her unable to walk without crutches. She sang the role beautifully, however, from the wings while the part was acted excellently by German mezzosoprano Marlene Lichtenberg. The customary awkwardness of the apparent ventriloquism was avoided by Lichtenberg's obvious command of the role and her ability to mouth the words to match Cargill's singing.

I was intrigued but not totally convinced by the rather minimalist geometric set design, originally created at Glyndebourne in 2003 by Roland Aeschlimann for the director Nikolaus Lehnhoff. Consisting mostly of incomplete concentric circles, it may suggest a visual equivalent of the unresolved Tristan chord, while also being a way to let Wagner's music tell the story without being distracted by a more striking set.

The production seemed subdued until the arrival of the German bass Franz-Josef Selig as King Marke whose passionate voice brilliantly conveyed the intense emotions of the tale. Both in singing and acting, he lifted the quality of the performance a notch or two.

Before Selig arrived, the most vigorous and consistent display of energy came from the conductor Robin Ticciati, who throughout this opera inspired the London Philharmonic Orchestra to give a marvellously passionate performance. They were the real stars of the day.

Tristan und Isolde is playing at the Glyndebourne Festival until 25 August. Box office: 01273 815 000 or glyndebourne.com