So what is modern art, Mr Serota?

It's a paradox that a man so evangelical about galleries is so hesitant about the quality of art

TODAY AT 11am today there will be a roof-top ceremony for the topping-out of Nicholas Serota.

Officially it's the completion of the new Tate Gallery of Modern Art at London's Bankside. But the country's first national modern art museum is, like the forthcoming conversion of the Millbank Tate into the world's biggest display of British art, Mr Serota's brainchild. Even the much- needed Thames riverboat service that will ferry art lovers between the sites is his idea.

The Serota effect spreads beyond the two banks of the Thames. As director of the Tate Gallery he is in overall charge not only of the two London institutions but of the Tate, Liverpool and the Tate, St Ives. As chairman of the Turner Prize judges he has a huge influence in determining what is judged to be at the cutting edge of contemporary art. Even when Britain is represented at major festivals abroad, such as the Venice Biennale, the bespectacled Tate director, with his sphinx-like expression, helps choose who shall represent the country as chair of the British Council committee.

His influence over art and artists is bigger than any comparable figure in any other art form in Britain. Perhaps for that reason it has not always been seen as benign. The late Peter Fuller, the founder of the leading art journal Modern Painters, labelled him the head of "the academy of the avant-garde", and The Spectator was certainly not alone when it claimed that "prevailing fashion, often of the most ephemeral kind, is effectively enshrined by events such as the Turner Prize and rewarded so blatantly by policy on acquisitions".

But Serota has overcome such criticisms through a highly imaginative series of actions which has helped to bring new audiences to contemporary art, a genre that is all too often the preserve of a metropolitan clique.

At the new museum of modern art at Bankside he has gone out of his way to involve the local working-class community in a project of which it was initially suspicious. Of the workforce involved in converting the former power station into an art gallery, 18 per cent have been recruited locally. Training courses are being run for the long-term unemployed. The area around the gallery is being landscaped into public space and gardens, a regular newsletter is delivered to 5,000 local residents, and, even before opening, the new gallery's staff has run workshops for local schools which have resulted in them designing banners for the neighbouring Globe Theatre.

And next Monday the exterior of the power station will be transformed into a giant screen for a programme of classic films and videos by Andy Warhol, Richard Serra, Julian Opie and others. This is Serota, community aesthete at work; and, allied to the talents and clear vision of Serota the fund raiser and manager, it explains why the pounds 130m lottery-assisted project has attracted more support nationally and locally than almost any other millennium project and why it has avoided the unpopularity and shambolic mismanagement of the Royal Opera House.

But there is another Nicholas Serota. It is Serota the cryptic, the oblique, the sphinx-like and, sometimes, the dismissive. These are characteristics I have witnessed when the Tate director is questioned about his acquisitions policy and, most particularly, the annual controversy over the Turner Prize, when he can be curt to those who dispute his championing of video art and of the many shock installations that characterise the "sensation generation".

It is a paradox that a man who is so evangelical about the buildings that house the art can be hesitant about engaging in argument over the quality of the art itself. The debate that has raged over whether painting is dead is unquestionably partly inspired by the constant lack of representational art on the Turner Prize shortlist. But where does Serota stand? He needs to address the debate and tell us where he stands on the future of painting in this country. Then there is the question of what will actually be displayed in the exciting riverside space at Bankside. Serota could mirror the local community involvement at Bankside with a national debate on what Britain's first national museum of modern art should contain. In that context we could hear his thoughts on the direction of contemporary art and an analysis of his own tastes.

He is about to present to the world a British view of the cutting edge. So far he hasn't put a foot wrong. But now he could render art and young artists a tremendous service by being as publicly evangelical, lucid and analytical about their work as he is about the building that will contain it.