Louise MacBain: The patroness

From Prince Andrew to Tessa Jowell, she has friends in the highest places. No wonder. She is pouring millions into the London art scene in a manner that befits the greatest philanthropists. But does this most elegant of blondes have substance as well as style?

When an elegant blonde French-Canadian multi-millionairess unveiled the advisory board of her new London-based arts foundation last week, even the most demanding of celebrity-watchers would have been impressed. Members included Damien Hirst, Jeff Koons, Mario Testino, Bianca Jagger, Susan Greenfield and the heads of Unesco and the Organisation for Economic Co-operation and Development (OECD).

When an elegant blonde French-Canadian multi-millionairess unveiled the advisory board of her new London-based arts foundation last week, even the most demanding of celebrity-watchers would have been impressed. Members included Damien Hirst, Jeff Koons, Mario Testino, Bianca Jagger, Susan Greenfield and the heads of Unesco and the Organisation for Economic Co-operation and Development (OECD).

Who could have had the power, wealth and influence to bring together such a diverse collection of stellar names? Step forward 46-year-old Louise Blouin MacBain, who some on the London art scene already believe has the makings of another Peggy Guggenheim.

The Louise T Blouin Foundation, which will have its £12m headquarters in Notting Hill, is being talked of as a rival to the ICA and "the Davos of the art world". In the three-and-a-half years since she arrived in London, MacBain has become a force to be reckoned with, even without her other claim to fame - a much speculated-on friendship with Prince Andrew.

MacBain has certainly got the London arts scene talking. She has breakfast with Henry Kissinger, dines with royalty, and has the ear of politicians such as Tessa Jowell. But is she really the next great philanthropist, or is she just out to make another fortune with her publishing company, which has been Hoovering up art magazines on both sides of the Atlantic? What exactly is the LTB Foundation going to do? And what is the truth about those Prince Andrew stories?

Charles Saumarez Smith, director of the National Gallery, speaks warmly of MacBain, as does the artist Antony Gormley, who calls her "an extremely good patron". Others in the London art scene are not sure. Some are baffled by her grandiloquent rhetoric; the mission statement of the LTB Foundation urges the establishment of "a new Renaissance" to "begin to address the world's problems", no less. Others are unconvinced because the foundation's headquarters will not open its doors until next year, and concrete evidence of its activities has so far been lacking.

What is known, however, is that she is worth £250m. That makes her an object of fascination in the British art world, where the prospect of receiving even a tiny fraction of that sum is sought after both by public galleries, which can rarely hope to sign up such wealthy patrons, and private galleries, which complain about the stinginess of British collectors. MacBain was born and raised in Montreal, where she attended an Italian convent school. "Everything in my life has been based on responsibility and discipline because of that and my parents as practising Catholics," she says. When she was 20 she had a brief first marriage, which was annulled. Later she married John MacBain, the son of a prominent Canadian family. They had three children and built a highly successful classified advertising business in North America, from which her fortune derives. Although they are divorced, she still describes him warmly as "an intelligent and brilliant man".

People in more fashionable cultural spheres started taking notice of MacBain when she bought Art + Auction, the respected art market magazine, in 2003. By the end of last year, her holding company claimed to have 165 publications in the US and Europe, including the UK's highly regarded Modern Painters. An internet site, artinfo.com, followed this year, and with the announcement of her foundation it became clear that Louise MacBain's ambitions were far from modest.

The speed with which she moved has aroused suspicion. Prior to her buying spree, MacBain was chief executive of the auction house Phillips, and the lover of its chairman, Simon de Pury - but before this was not known for her interest in art. When she parted after two years from both De Pury and Phillips, and embarked on her new career as an art publishing mogul, some suggested she was motivated by revenge.

MacBain disputes the allegation. "I think Simon's great," she says. "I never meant to stay there, I just went to help." To those who doubt the depth of her interest in art, she points out that she was a volunteer at the Montreal Museum of Fine Arts when she was 23 and that she is a long-standing collector. The garden of her Holland Park house contains an Antony Gormley sculpture, and she also owns works by Hirst and Wolfgang Tillmans.

This is the same house in which a tabloid newspaper recently claimed that, last October, Prince Andrew "ended their year-long affair after one final night of passion ... leaving her bewildered and embarrassed". The newspaper alleged that MacBain referred to the prince as her "boyfriend"; that she accompanied him to a gala dinner at Kensington Palace (she turned up late and disrupted the seating plan so she could be next to him); that he stayed with her at her house in the Hamptons, where they sat "toasting marshmallows in the moonlight"; and that "her enthusiasm led her to believe it would end in marriage". Asked about the article, MacBain said that she never commented on her private life, but described it as "probably 40 per cent wrong". That left the other 60 per cent of an article which made no attempt to hedge the issue of an affair. Expressing shock at the piece, she said: "It tells me how much we need more art, because it motivates us to give better values to the people who go out there and write whatever they want without checking the facts."

This kind of high-blown talk leaves many confused. Her foundation aims to combine charitable and educational work with research, particularly into the effects on the brain of art, a range that strikes some as dangerously unfocused and woolly. Her habit of bandying the word "creativity" about is all very well, but when MacBain makes claims that her internet site will be able to give "hopes and dreams" to poor people in Africa, her stock of credibility diminishes in the eyes of her critics, one of whom accuses her of speaking "complete whiffle".

"In America, it's very common for individuals to set up well-funded foundations named after themselves, but not here," says an executive at another art publication in which MacBain took an interest. "People are suspicious of her." With her designer-clad figure (honed by an hour's pilates every morning), wealth and extraordinary networking skills (Bill Clinton made a video link appearance at last week's dinner), MacBain is an exotic and unknown figure. She is neither a pure collector like Charles Saatchi, nor an expert like Nicholas Serota or Norman Rosenthal. Although her fortune gives her enormous potential power, the London art world cannot grasp to what end she will put it, and remains wary.

"I'm an individual to help talent and creativity," she said recently. "I don't do this for power. I have everything I want in my life. I do this to make a difference." It is up to Louise MacBain to prove that she can, for there are plenty of cynics waiting for her to fail.