It is ten years since the Guggenheim Museum in New York pulled off its greatest expansionary cultural coup: opening the new Guggenheim Museum in a superb Frank Gehry building in the industrial city of Bilbao, in the Spanish Basque country. Ten years in which countless other cities have sought to rebrand themselves with bold new architecture; ten years in which Thomas Krens, the colourfully controversial figure who has headed the Guggenheim since 1988, has circled the globe as the institution’s energetic and entrepreneurial ambassador, searching out fresh horizons for yet more expansion. Now Krens is back in town to celebrate the anniversary of one of his most audacious successes.

However many times you have visited Bilbao in the past ten years – and Krens says he has flown in perhaps 100 times – the building casts a fresh spell every time, and this is surely one measure of its greatness. It has weathered well: its titanium panels remain unscarred by a decade of intense heat and bitter cold, and it still looks beautiful in today’s withering grey drizzle. Inside are many temptations, the most intensely dramatic being Richard Serra’s The Matter of Time, a permanent installation of seven huge steel sculptures, coursing with unpredictable energy, and opening today is Art in the USA: 300 Years of Innovation, a Guggenheim show which has come to Bilbao via China and Russia.

This morning, Krens has done his duty at a press conference to mark the anniversary and launch the exhibition. But word is circulating that he is in a particularly cranky mood, that he has flown in from somewhere – could be Russia, could be China, maybe Venice, no one is quite sure – that he is exhausted and hasn’t even yet had a coffee. Anxious staff circle and hover. There is an atmosphere of imminent disaster. So when Krens announces that we are to go and have lunch at his favourite restaurant, there is palpable relief all round.

Krens is 6ft 5in tall, tanned, with white hair, and today wears the sharply austere uniform of a leading international art world figure. In spite of, or perhaps because of, the low expectations of fun, he turns out to be rather jolly, though not a polished performer, having generally kept his distance from the press for fear of forever being cast as the Villain. He’s not at all precious, however, always ready for a scrap, and he has about him a battle-scarred plenitude. Neatly folding himself into a taxi, and along the way pointing out a “Fosterita” (one of the subway stations designed by Norman Foster) and a bridge by Santiago Calatrava, he directs the driver to a family-run restaurant tucked away in a fine square in Bilbao’s old quarter.

The moment Krens walks in, looking all about him from a great height, the staff surge forward with obsequious smiles. After much emotional embracing and showing of snapshots of grandchildren, we eventually reach our table. Wine and jamón are ordered, and Krens sits back to survey the scene. “When it became known that this was my favourite restaurant, the place grew and grew,” he says. “Victor didn’t own a suit until I started coming here. I even have my own wall of photos.” He waves at a wall of fading snapshots, which do indeed show Krens on various occasions: with his 16-year-old son, with wealthy museum trustee types, and with Jeremy Irons, with whom he goes off on motorbike trips three or four times a year.

Krens, 60, is a powerful but controversial figure in the art world. Clever, articulate and with a sharp business brain (he has an MBA from Yale), plus 17 years paying his dues as an art academic, as the director of the Solomon R. Guggenheim Foundation he now plays many roles. He is in charge of strategy, he is the chief fundraiser, the man who courts wealthy art lovers. He is also chief artistic officer, in charge of acquisitions and programming for all Guggenheim museums around the world. These now number five: the original Guggenheim Museum in New York, founded in 1937 by the American mining magnate and philanthropist Solomon R. Guggenheim, the Peggy Guggenheim Collection in Venice, mostly housing the 20th-century art accumulated by Solomon’s niece, plus the Guggenheim Museum Bilbao, the Deutsche Guggenheim in Berlin and the Guggenheim Hermitage Museum in Las Vegas – these last three all opened during Krens’ tenure at the Guggenheim Foundation.

Krens sometimes also curates some major exhibitions, and all this clout, combined with a larger-than-life personality and a matching ego, tends to polarise opinion in the museum world. “My personality tends to create this wedge,” Krens agrees. “Some people think I’m the second coming of the devil. Others think I’m the wave of the future. But I prefer to focus on actions, not words.” The actions – which have at times been daring to the point of risky – have appalled some and thrilled others, all the while provoking a degree of envy among that small coterie of top international museum directors who are more bound than he is by the rules of their institutions.

For Krens is marked out by his willingness to transgress the established conventions of museum directorship, and that clearly riles some of his rivals. Following the opening, ten years ago, of the Guggenheim Bilbao, Krens orchestrated the opening of the Guggenheim Berlin the same year. Then in 2001 he signed a long-term collaboration agreement with the Hermitage in St Petersburg to make the collections of the two museums accessible to a broader audience, the same year opening the Guggenheim Hermitage Museum and the Guggenheim Las Vegas in two new galleries – designed by Rem Koolhaas – inside the Venetian casino resort in Las Vegas. The press was immediately all over Krens like a swarm of gnats and the critical ridicule came in torrents. Art critic Chuck Twardy described Krens’ vision of the Guggenheim as “flashy, voguish, mile-wide and skin-deep… the museum as shopping experience”.

“When you’re in the missionary business, which we are,” Krens responded crisply, “you go where the heathens are.” Unfortunately for Krens, the heathens proved immune to conversion and half of the development, the Guggenheim Las Vegas, had to close down 15 months later. In Rio de Janeiro, Krens would get as far as signing a contract to build a Brazilian Guggenheim, designed by Jean Nouvel, when local political opposition scuppered the project.

“I receive requests from ambitious mayors in cities all over the world who have seen what the Guggenheim here has done for Bilbao [which now gets one million visitors a year, this in an otherwise unremarkable post-industrial city of 500,000]. I get them from everywhere. So if there is potential, we send in a team which does a feasibility study, for which we get paid, and we’re getting very good at this now. We look at the financial questions, the social mix, the physical and logistical set-up; we look at what art collections there are in the region. [Krens has one eye constantly focused on adding to the Guggenheim collections, which have doubled in terms of number of objects since he took over.] But it’s a big thing. There’s a $600 million price tag for a Bilbao, you know.

“The Rio project fell apart five days before the contract was triggered. The same thing almost happened in Bilbao. We came within a whisker of the project evaporating because of political opposition. And then when this happens, the reaction is, ‘Oh look. Tom’s failed.’ But I think, if you get on base 30 per cent of the time, then you’re one of the most valuable players in the league… With more experience, we get better at learning how to manage the risks involved.” Krens has considered building Guggenheims in Salzburg, Macao, Hong Kong, Singapore, Beijing, Taiwan, Tokyo, Osaka, Mexico and St Petersburg. He hopes one day to open another Guggenheim in Manhattan – although the short-lived Guggenheim SoHo annexe closed after 9/11 – in order to free up space at the Fifth Avenue building for more of the pre-war permanent collection and to attract donations of important private art collections on which the museum’s future survival depends. None of these efforts has yet succeeded, but Krens is undeterred.

But this notion of turning the Guggenheim into a global cultural brand isn’t without its critics. Alain Sayag, chief curator at the Pompidou Centre, has compared the Guggenheim to a Coca-Cola franchise. Anna Somers Cocks, editor of the Art Newspaper, compares it to McDonald’s. Nicolas Serota is more cautious: “Krens is surprisingly energetic,” is all he will say, while Philippe de Montebello, director of New York’s Metropolitan Museum, declines to comment.

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