Britain greets its newest art treasure

If it's in an art gallery then it's art, according to one line of thought. And if that is true there is little doubting which work was the centre of attention at Britain's newest and biggest art gallery yesterday. The site was Tate Modern and the title of the temporary installation was Official Opening - a mixed-media performance piece involving a low podium, two microphones, a 74-year-old monarch and a large assembly of the cultural great and good.

It began to the sound of amplified birdsong, the prelude to a specially commissioned fanfare by the com- poser Harrison Birtwistle which accompanied the Queen down the immense ramp that leads into the converted Bankside power station from its western entrance. As eerie, clanging antiphonies played knowingly with the echoes of Gilbert Scott's vast Turbine Hall, the Queen remained resolutely deadpan and the composer looked pensively at the floor, carefully attentive to the London Sinfonietta's performance of his piece.

Official Opening was not a work that gave up its meanings readily - what exactly was passing through its performer's mind as she listened to the chairman of the trustees, David Verey, hail a "historic day for visual arts" and a milestone in European culture? Was there a surreal intention in this collision of Royal Enclosure glamour (eau-de-Nil twinset and a Walnut Whirl of a hat) and Modernist severity (black steel girders and concrete floors), or did it mark a genuine rapprochement between high society and high art?

But if the Queen had brought a speech pledging the House of Windsor to further the cause of conceptual art, then the grandeur of the surroundings had robbed her of the capacity to deliver it. Smiling only briefly as Mr Verey finally gave her cue, she restricted herself to a single, non-committal utterance - "I declare Tate Modern open" - before leaning forward to press the button in front of her.

A hundred feet above her head one of the hall's original gantry cranes, built by Sir William Arrol & Co of Glasgow, was poised to spring into action. The working load on the main hook is 20 tons - which must have come in handy during the installation of Louise Bourgeois's looming sheet-metal watchtowers, and the 30ft steel spider which crouched above the Queen on the building's crosswalk. But nothing like that lifting capacity was required for its sole task yesterday, which was to raise a minimalist version of the traditional red velvet curtain. As a marimba flourishmarked the moment, everyone turned to watch expectantly. The cubist veil rose six feet, revealed the commemorative inscription, and halted. The work was over.

But if there was a faint sense of anti-climax to this conclusion, the Queen's fellow performance artists Gilbert and George were highly complimentary about her execution of the piece. "She looked lovely," said George approvingly; "And she pressed the button very well," added Gilbert.

The former seemed mildly disappointed that they were not among the artists selected to meet her - they did have a piece in the gallery entitled England, after all. But the Queen's brief tour of the gallery with Sir Nicholas Serota, Tate director, plotted a cautious course well away from the more awkward parts of the collection. The royal eyes would not have to be averted from Matthew Barney's video work (in which a naked man pushes objects into various bodily orifices and is filmed collapsing to the floor) but could rest with reasonable security on one of Monet's lily paintings, or the more established modernity of Bridget Riley, with whom the Queen apparently talked for some time.

Downstairs the other guests waited for their turn to view the galleries, a buzz of conversation almost drowning the steady hum that comes from behind the building's south wall, where working transformers occupy a space already being covetously eyed by artists and some Tate curators. The verdict was almost unanimous - at last a grand cultural project had been brought home on time and within budget. Modern art appeared to have crossed the surprisingly narrow corridor that divides a national joke from a source of national pride.

In the general mood of jubilant satisfaction, David Verey's claim that Tate Modern represented "a new start for visual arts in this country" did not seem at all far-fetched.

Much later a waiter cautiously made his way through the crowd with a 6ft length of cornicing, stacked from end to end with miniature lamb samosas. Anywhere else this would have been just another round of canapés, but under this roof, and in this company, it suddenly seemed altogether more suggestive - not so much an impromptu platter as an interrogation of a Britain poised between its love of traditional detail and a new imaginative openness.