The enthralled Liu bought several pieces and made it a point to get to know the artist, who has now become a good friend.

Although Liu was buying primarily for pleasure, the value of her acquisitions soared as international auction houses such as Christie's and Sotheby's began taking an interest in Chinese contemporary art. The 40-year-old chuckles heartily - and incredulously - as she recounts how the estimate for one of her Zhang Xiaogang paintings rose twentyfold after a few years.

'For me that is just incredible,' she says. 'Between 2003 and 2005, the cost of paintings was about US$30,000 to US$50,000. Then prices took off - after 2006 they just rocketed. One painting which I bought for US$30,000 went up to US$700,000 just two years later.'

While Liu claims she hasn't got a grip on how much her collection is now worth, the Zhang paintings alone would add up to US$20 million and she is clearly making shrewd acquisitions based on artistic merit rather than faddish whims. 'My first priority is always the work itself. I have to love the art,' she says. 'I then check on the artist, what work he has done before, about his experience and his place in the art world. I need to know what he is likely to do in future - some artists disappear some years later.'

Liu was raised in a vibrant cultural environment; her mother Wang Shuping was an actress and recited Shakespeare to her as a child. Unusually for a mainlander during the early 1980s, she had access to films from the United States and Japan - a perk thanks to her father, film director Liu Zilong. She later spent five years studying French at the Sorbonne. One of her sisters, Liu Jie, married a French photographer and went on to write the bestselling memoir, No Tears for Mao, under the pen name Niu Niu.

Originally published in French, it was a harrowing tale, which described her grandfather being beaten to death by Red Guards, and how her parents were exiled from their home in Chengdu for re-education in the countryside while their grandmother struggled to care for the children.

Liu Lan says she has little personal recollection of that period - and has even less inclination to talk about it. But she adds that her parents were proud and happy that one of their daughters had become a published author, albeit with a subject that brought back some painful memories.

In the thaw after the Cultural Revolution, her father built a successful career in film and television, directing several popular movies including Song in Whirlpool and Ripples across Stagnant Water. 'I got a love of film from my father,' Liu says. 'When in Paris, I once counted how many movies I saw in a year; I think it added up to almost 200. Almost every day I went to cinema or museums.'

Another sister, Liu Qian, a trained dancer, later also emigrated to France, where she now runs an art gallery near the Louvre.

Liu Lan returned to the mainland in the early 1990s and later married entrepreneur Hu Xiaolin. The couple began a heating-appliance business, initially importing boilers and parts from Europe. This grew into Beijing H.T. Technology Develope Company, which manufactures and installs heating equipment.

While the global appetite for contemporary Chinese art has led many new collectors to assemble impressive portfolios in rapid time, the best private collections are widely acknowledged to be those belonging to former Beijing-based diplomat Uli Sigg and Belgian billionaire Guy Ullens, who carefully acquired works over many years.

On the mainland, Liu's steadily growing collection, which is displayed in rotation at her offices and home, is one of the most notable. The public had a glimpse of its strength when she exhibited part of the collection two years ago at Beijing Commune, an alternative art space founded by her friend and personal art adviser Leng Lin. 'It's a collection of real quality, with some very important pieces, especially the earlier work of Zhang Xiaogang,' says Leng, who also heads the Pace Gallery in Beijing. 'She started buying pieces early on, learned very quickly and developed a very good eye.'

Among the gems are Tiananmen No. 2, a dark, thought-provoking painting by Zhang Xiaogang, Romanticism and Realism Study No. 6 featuring the grinning, toothy characters favoured by Yue Minjun, For the Yellow and Blue of M, a delicately hued work by Liu Ye, and Sky, a beach scene by Zeng Fanzhi.

'My collection is constantly changing,' says Liu, whose most expensive purchase was A Big Family by Zhang, which cost her US$2 million at auction. 'It's like the plot of a play, with different characters that change. Recently I have added sculpture and video to the collection: I really like Yang Fudong's video work. My attitude to art is very different from the approach I adopt during my professional work. With the company, I am very serious, very meticulous and very process minded. But art is a chance to have a rest, another way to see the world and to have a different image of the world. With art I totally relax.'

Although she regularly shells out significant sums for provocative art works, Liu is not generally given to flamboyance in her personal life. And while her husband doesn't share her passion for art, he, too, prefers more modest living: his way of winding down after work is to read texts on Buddhist philosophy.

At their company headquarters in a utilitarian office in Beijing's financial district, the only clues to the couple's interests are a small selection of paintings on the walls, a Buddhist shrine in the office and a music system playing soothing chants.

Says Liu: 'In business you can make money, but you don't get pleasure from money itself. With art, there is pleasure and passion.'

Liu's parents died before her collection really took shape but she is convinced they would have understood her passion for contemporary art, though they would have found it difficult to comprehend some of the stratospheric prices. 'When my mother was alive I paid US$30,000 for a painting but was afraid to tell her because she would think it was too expensive,' she says. 'So I told a white lie and said it cost around $3,000 - and she thought that was expensive! I put it on the wall at home and at first she didn't like it, but after two days she started looking at it seriously and, day by day, she told me she loved the painting and that made me very happy.'