Welsh National Opera is at its brilliant best in this summer’s revival of Yannis Kokkos’s production — he both directs and designs — of Wagner’s Tristan and Isolde. The performances at Wales Millennium Centre cannot fail to invite comparison, far from odious, with the production as originally staged 19 years ago with Sir Charles Mackerras in charge and that great Wagnerian Anne Evans as Isolde. Phillip Joll who sang Kurwenal just once in 1993, at the performance at Oxford’s New Theatre, returns to the role in Cardiff, again in excellent voice. Susan Bickley, who impressed Oxford audiences as Brangäne in the 2006 revival, offers another assured and affecting performance.

WNO’s music director Lothar Koenigs comes new to the opera after his stunning success two years ago conducting Die Meistersinger. Once again, he exercises impeccable control of the vast forces under his control, the work’s many delicate passages contrasting tellingly with moments of thrilling drama when brass blares and drums roll.

The work of cor anglais player Max Spiers supplying the haunting melody for the shepherd’s pipe in Act III is especially praiseworthy, as, too, is that of sweet-voiced tenor Simon Crosby Buttle, plucked from the WNO chorus to portray the shepherd.

But it is to the singers in the two title roles, of course, that the opera poses the most formidable challenges. To these rise superbly the Canadian tenor Ben Heppner — clearly fully recovered from the vocal problems that led to his withdrawal from last year’s Metropolitan Opera Ring — and the Danish soprano Ann Petersen, making her British debut.

Magnificent as the seemingly endless Act II love duet is here (would that It did last for ever), even this lacks the emotional heft of Ms Petersen’s Liebestod, at the close of which she stands transfigured, steadily disappearing from view in a dimming spotlight (design Guido Levi/realisation Paul Woodfield).

This is a production in which the acting never matches the quality of the singing. Revival director Peter Watson might, for instance, have done something about the lovers’ sudden comic collapse, like felled trees, from the effects of the fatal potion, and the no less absurd ‘stab, stab; you’re dead’ of the fight scenes.

There are further performances in Cardiff on Saturday and at Birmingham Hippodrome on June 16.