Given the circumstances, it seems a courageous line to take. Lockhart Saatchi is sitting in the National Gallery cafe on a wet Wednesday morning, mulling over a cappuccino and the question of which of the world's artworks she would choose to have if given her pick of them all. This is not as whimsical as it sounds. The National Art Collections Fund (NACF) - a charity that has been buying works for British public galleries since its acquisition of Velazquez's Rokeby Venus for the National Gallery in 1906 - has persuaded Lockhart Saatchi and three other celebrities (including the aforementioned Brian Sewell) to put together fantasy collections and then to lecture on them. If you subscribe to her view of art collecting as a species of autobiography, then Lockhart Saatchi - a famously private woman - is laying her life on the line.
Once upon a time, that life seemed little short of blessed. Married in 1973 to Charles Saatchi - partner, with his brother Maurice, in the billion- pound ad agency of those names - the Sorbonne-educated Doris Lockhart set about putting together what was to become the most important private collection of contemporary art in Britain.
In 1984, the Saatchi collection - its particular strength in American minimalist painting ascribable more to Doris's eye than to her husband's - moved to its own gallery in St John's Wood and became The Saatchi Collection. Then, in 1988, Charles Saatchi left his wife. Two years later he divorced her, married another woman and - having had no children from his first marriage - fathered a daughter. Something of the nature of their divorce may be deduced from the fact that Charles Saatchi's current entry in Who's Who makes no reference to Doris Lockhart's ever having even existed.
The potential shock-value of her fantasy collection is suggested by the title of the lecture she will deliver on it: Going for Baroque. She might as well have called it The Shock of the Old. The woman whose (married) name was once a synonym for all that was contemporary in contemporary British art ticks off her choices so far: Zurbaran's Saint Francis in Meditation, next door in the National Gallery; Simone Martini's Uffizi Annunciation, one each of Delacroix, Ingres, Bruegel and Poussin, although she hasn't decided which yet; Warhol's Triple Elvis; and - the only work by a living (although hardly by a young) artist - an as yet unspecified piece by the American mimimalist painter Brice Marden.
Her advice on the whereabouts of the last of these works suggests a rather better-mannered riposte to her ex-husband's rewriting of their marital history. In that polite East Coast drawl that pronounces "art"' as "aht" rather than "ard", she says, "The trouble is that the Saatchi Collection is now a very different thing from when I had anything to do with it. I don't really know if there are any Brice Mardens still left in it. I guess Charles Saatchi may have de- acquisitioned them. That" - she smiles a helpful smile - "is an art-world euphemism for 'sold'."
As to The Collection's legacy, Lockhart Saatchi is more than willing to acknowledge her husband's role in shaping the British art world's current tastes. "In 1988 I lectured at the Royal College of Art and I was appalled at how careerist the students had become," she winces. "They all wanted to get work into the Saatchi Collection, so they were making huge things to fill all those huge spaces. So un-British: well, pace Turner, anyway. We live in a time that is heavily influenced by advertising and, as we all know, Charles Saatchi is a master of that discipline. The influence is felt in much of the art made today, and, for me, it's soft at the centre. I don't want narrative, but there's a lack of rigour in it."
If all this suggests that the genius of Lockhart Saatchi's NACF collection is not so much pre- contemporary as post-marital, then her analysis of its constituent parts seems openly (not to say painfully) confessional. Of the Simone Annun- ciation, for example, she remarks, "I'm not a believer, but I don't think that matters. To me, the miraculous thing about that painting is the expression on Mary's face: the fear, the foreknowledge of the pain she's going to have to suffer. Of the loss."
Doris Lockhart was writing on Ingres at the Sorbonne before she had heard of Charles Saatchi: her NACF fantasy works are less an anithesis to her past life in art than a synthesis of it. What she refers to as the "personal narrative" of her hypothetical collection is still underpinned by a taste for the new. The Simone Annunciation, whatever the Virgin's woes, is "a very modern painting - maybe the first piece of genuine minimalism". The Zurbaran - "It's hard to talk about art without sounding like a jerk," says Lockhart Saatchi, sheepishly - appeals because of its sparseness: "It's the way that everything is pared down to blocks of light and shade: that the entire narrative becomes one black hole for [St Francis's] mouth and two for the skull's eyes. "
Biographical nosiness is not the only reason for reading the artistic runes in all this. Lockhart Saatchi's influence on contemporary British art is hardly diminished. She is a council member of the Architectural Association, a contributing editor to Blueprint, a sometime Late Show presenter and a juror for art prizes. She curates major exhibitions. And, most eye-catchingly, she is art consultant to the Millennium Dome's Mind Zone section, commissioning the works that will fill a space designed by the architect Zaha Hadid. In simple historical terms, in other words, Lockhart Saatchi will help define what we come to think of as millennial art.
Whatever the animus behind her views, they count. When she speaks - as she does, acutely and movingly - of the millenarian search for meaning in the "majesty and mystery of the inner workings of a cow", Damien Hirst can rest easy. While she is an unapologetic advocate of personal influence - recently causing a stir at the Contemporary Arts Society by suggesting that they become "less democratic" by giving more power to individual curators - she is, perhaps a touch disingenuously, modest about her own. Of the two women - Isabella d'Este and Diana the Huntress - who recur in her artistic conversation, Lockhart Saatchi identifies, surprisingly, with the latter.
"Isabella was a classic rich, powerful woman," she says. "A matriarch, the head of a grand family. I don't see myself like that at all. I'm more like Diana. As Artemis, she lived on the mountain- tops. But she also lived alone. I guess that's a description of me."
Doris Lockhart Saatchi's lecture is on Tuesday 3 Novem-ber. For details call the NACF on 0171 225 4800.