Beautiful, nostalgic, infuriating: the British premiere of the five-hour Einstein on the Beach by Robert Wilson and Philip Glass at the Barbican on Friday night was quite an occasion, not least for the technical hiccups.

Normally, scenic glitches would not matter too much, but as this extraordinary 1976 piece is all about aesthetics - in a way that simply nothing else in our theatre today ever is; the avant garde's over, remember?  - the wobbly scenery, too-visible stage managers (palpably not choreographed by Lucinda Childs) and failure of the flying arrangements - the evening was semi-seriously marred.

Not that this seemed to worry Robert Wilson himself, who appeared during an enforced ten minute interval break to explain that the last scene would not have all the intended effects: he was delighted, he said, to see so many happy smiling faces, including that, no doubt, of Bianca Jagger, stunningly attired in black silk and huge jewellery, who was apparently taking flash photography during the performance.

I noticed one or two flashes, but this sort of thing happens all the time at rock concerts, and nobody cares, and Einstein is so slow and so deliberate, and so broad-brush in its presentation,  that the scenic shortcomings were far more disruptive than the odd flash in the audience.
 
Anyway, Wilson beamed away and thanked us for coming: "Fasten your seat belts and have fun." Which, on the whole, we did. The lighting was slightly affected by the technical problems, but most of it was amazing, as were the two great set dance pieces by Childs - with a pang you realise how far in advance this choreography was of both Pina Bausch and Mark Morris - as well as the plangent playing and rapidly articulated singing of the Philip Glass ensemble in the pit, and on the stage in the courtroom scene.

Only at one point did the circular repetitiousness of Glass's score become a little trying, and that was during a really rather rubbish organ solo as a white strip of lighting was slowly hoisted into the vertical plane and Rupert Christiansen of the Daily Telegraph responded by ostentatiously holding his head in his hands in despair. 

Otherwise, the disjointed text, the beautifully composed images, the touchingly extravagant low-tech scenery of a night train, a moon, a virtuoso violinist Einstein in a big scraggy wig, the mathematical precision and allegory of it all, the stunning finale (even without the flying) of an atomic nuclear factory manned by automomatons and lit by a thousand blazing bulbs - all came momentously together... nearly.

The audience was invited to come and go as they pleased. The fact that they did so - some of them must have had dinner for an hour or two - was far more disruptive than the flash photography but, again, the show seemed to absorb the upheaval, no problem.

The strange, jagged concrete poetry is written by Christopher Knowles, whom I first saw at work with Wilson at a festival in Shiraz, Iran, in the pre-revolutionary mid-1970s. (Critics like myself who accepted invitations were accused of "propping up the Shah's regime"; if only we'd propped it up even more!)

Knowles was an autistic teenager (he's still a regular collaborator) whom Wilson had in effect adopted, and they produced a haunting, disturbing piece of theatre of just forty minutes length that was in deliberate contrast to the previous Shiraz Wilson show in which the audience had traipsed over a mountaintop for seven days. What's six kicks - or five hours! - to a man who's read Seneca, indeed? 

It was at one of those Shiraz festivals that Wilson's formidable agent, Ninon Karlweis, had fallen asleep in the front row of an outdoor Victor Garcia production lit by torches and set her own extravagantly coiffured hair on fire. That festival mood was maintained at the Barbican with the obligatory delayed start, the milling "up for it" crowds - the Barbican was packed to the rafters - and Bianca with her camera.

The audience also included Miranda Richardson (with Richard Wilson, no relation), who gave one of her greatest performances at the Edinburgh Festival of 1996 in Wilson's version of Virginia Woolf's Orlando.

Otherwise, we've been starved of his work over the years, having to make do with a lesser off-cut of Einstein, I Was Sitting On My Patio This Guy Appeared I Thought I Was Hallucinating, and, also at the Barbican, his brilliant collaboration with Tom Waits, The Black Rider

Wilson and Glass took a curtain call on Friday night to a rapturous reception and standing ovation. Partly this was to do with the great enthusiasm for Glass these days - his Ghandi opera, Satyagraha, which he wrote almost directly after Einstein, was a massive hit at the ENO recently (although it drove me nuts); but mainly, I think, it was a belated British acknowledgment of two supreme artistic innovators, now in their seventies, who both created work that is unrivalled in our theatre today, and who continue, paradoxically perhaps, to exert a massive influence.