Gawain review – fully restored, pointlessly staged, superbly performed version of Birtwistle's fourth opera

There are celebrations to come later in the year at the Proms and at the Southbank Centre, but the Barbican has got in first with its five-concert tribute to Harrison Birtwistle to mark his 80th birthday. It's a superbly well-planned retrospective, concentrating on pieces that not been heard here for some time. Unfortunately, there was no room (or the resources, I'd guess) for Birtwistle's monumental masterpiece, The Mask of Orpheus, but the series did begin with an almost equally massive score, his fourth opera, Gawain, first staged at Covent Garden in 1991 and not seen in the UK since its last revival 14 years ago.

In fact, it is even longer, since the score that Martyn Brabbins and the BBC Symphony Orchestra presented with such astonishing clarity and unerring sense of dramatic shape here was heard in its entirety; this concert staging restored the cuts to both acts that Birtwistle and his librettist David Harsent made for the revivals. About half an hour's music has been reclaimed, most of it in the cyclical masque of the seasons that forms the climax of the first act, with its off-stage unaccompanied motets and writhing, wrought orchestral writing. It's magnificent stuff, but including all of it does nothing for the opera's pacing or the sheer length (over three and a half hours) of the evening.

Even in the shorter version, this retelling of the dark-ages story of Gawain and his journey from Arthur's court to fulfil the challenge of the mysterious green knight is a formidable work to experience – musically often extraordinary, but sometimes hard to take dramatically. It's the most Wagnerian of all Birtwistle's scores, and even the story itself has Wagnerian resonances. Gawain himself is a kind of Parsifal figure; the two women, Morgan le Fay and the Lady de Hautdesert, recall Kundry; while the Green Knight and his alter ego Bertilak are some ways like the Ring characters of Hagen and Hunding, respectively. The orchestra is huge – there are three tubas, a vast percussion section and a cimbalom adding a special tang to thesound world, by turns darkly forbidding and gleamingly sensuous – and the sense of epic unfolding is hard to mistake.

Though the sheer scale of the work would have been hard to encompass in the confines of the Barbican Hall's platform, the concert staging designed, devised and lit by John Lloyd Davies added nothing whatsoever. One felt for a cast that worked so hard vocally, singing from scores, while having to enact the village-hall theatrics that Davies had come up with, and one longed for all of that to disappear, and for the cast to be allowed to just stand and deliver.

For the performance under Brabbins was in many respects exceptional. Only the indomitable John Tomlinson had sung his role (the double one of the Green Knight and Bertilak) before, both at Covent Garden and in last summer's production at the Salzburg festival. Leigh Melrose was Gawain, charting his character's personal journey from cocksure innocence to pained experience very surely; Laura Aiken was a wonderfully compelling Morgan le Fay, Jennifer Johnson her partner in seduction, De Hautdesert. Jeffrey Lloyd-Roberts was the terminally bored, emptily heroic Arthur, while Rachel Nicholls made every phrase of Guinevere's role matter. They all deserved a better dramatic framework, or even no such framework at all.