If Peter Fleissig asks you to look after a piece of art from his extraordinary collection, just say yes. Your house could soon become part of his `nvisible museum'. By Robin Muir
The photographs of artworks on these pages reflect the lifelong interest of collector Peter Fleissig in painting, drawing, sculpture, u-matic film loops, video installations and photography. He has works in mixed media too, such as a photograph by Matthew Barney with a "self- lubricating plastic frame". In his collection there are works on paper, unlimited plaster multiples - as well as a set of six chairs in fibreglass and steel by Simon Starling and one of Callum Innes' "exposed" paintings. An early sculpture in plaster, Fort (1989) by Rachel Whiteread is currently on loan to the Liverpool Tate.

He calls it "recycling". His first acquisitions were mainly drawings by sculptors, and from this period he has early works by, among others, Richard Deacon and Richard Long. They are, he says "about how to define invisible spaces", and his collection is known invariably as the "nvisible collection" (the first "i" is not there as in, well, invisible). It is invisible, at least to him, because he has chosen to lend out his works - mostly acquired from artists at the beginnings of their careers - to friends and other artists and occasionally, like the Whiteread sculpture, to museums, to create, he says "an invisible mental museum inspired by Andre Malraux's concept of a museum without walls: a sort of invisible museum across London, which celebrates art in unconventional contexts".

His most recent acquisition is a 1998 offset litho print by Emma Kay, Bible (from memory) - for which he paid just pounds 250 - reflecting the "spiritual theme" to the works he has accumulated since 1994. After the drawings by sculptors and others, the focus of his collection shifted to "younger artists, not the biggest or the shiniest works (the price never more than a second-hand Saab) but the kind of works museums wouldn't buy". Conceptual artist Mark Pimlott thinks that his drawing of a collapsed box has the "distinction of being the cheapest thing Peter has bought".

Many of the artists whose work he has collected have become his friends, as have most of the critics, private gallery owners and museum curators in London and beyond (he lives for the most part in New York). As he is still young, there is a lot of interest still to be stimulated, a lot more artists to become friends and a lot more art to be "recycled". A sometime writer (he was the art critic for the now defunct City Limits magazine for four weeks) and a student at the Architectural Association in London, he has been at the forefront of the British art scene for a long time. He was photographed, among 30 others, for a prescient piece, The British Art Buzz, for Vogue in 1995. Selections from his holdings have been shown in Kiev and will be seen in Birmingham Alabama in the New Year (it is about "migration and collecting in the year zero"). In the meantime, in the week when Charles Saatchi disposes of many works from his collection, a show of Peter Fleissig's - "Family" - opens in Edinburgh.

Fleissig has an exacting and eclectic eye and is almost absurdly modest. He does not crave any recognition for himself which is why you probably won't have heard of him. He agreed to this article, and to waive his anonymity (he is not mentioned by name on "Family's" press release or invitations) to support Inverleith House in Edinburgh, the show's venue.

And it is plain to see why. Heading towards the north of the city, set in its Botanic Gardens, it is a stunning setting for contemporary art and probably unique, for its programme is run by a fully qualified botanist. For most of this century, Inverleith House, built in 1774, was the private residence of successive directors of the Botanic Gardens but in 1959, one of them, Professor Sir Harold Fletcher, responded to the need to establish the first Scottish National Gallery of Modern Art and gave up his house accordingly. As Paul Nesbitt, its current director of exhibitions (and fully qualified botanist) puts it: "Fletcher saw fit to relinquish his privilege in the name of art. During that time many people, especially children, were introduced to modern art for the first time - including Callum Innes, who can still recall, as I can, the exact positions of the paintings of Picasso and Matisse on the walls." Nesbitt's group shows read like a survey of 20th century art and photography with major bodies of work by Warhol, Ed Ruscha, Man Ray, Cindy Sherman and Robert Mapplethorpe. He has recently curated one person shows by Carl Andre, Callum Innes and Tina Modotti.

For Fleissig's collection, usually lining the walls of other people's houses, this is an apposite venue. Perhaps envisaging the settings he might find them in should he tour their current whereabouts, he has arranged his family of pictures at Inverleith House to reflect the domestic layout that, as a private residence, it might once have had. So a tour of "Family" would find Bernd and Hilla Becher's generic image of a terraced house, House (1989), in the entrance hall; Sam Taylor-Wood's Five Revolutionary Seconds III (1996) in the stairwell; in the dining room, Starling's white chairs and the Callum Innes (Resonance XII) and on through the drawing room past the shark drawing by Hirst and two living rooms from the 1950s reinterpreted for the 1990s by Richard Hamilton; upstairs and left is the billiard room and works by Douglas Gordon and Richard Billingham; in the library find Bible (From Memory) (1998) by Emma Kay; in the teenage bedroom Georgina Starr's video Crying (1993) and in the parents' bedroom, Billingham's untitled photograph of his mother and Rachel Whiteread's Untitled (Study for Concave and Convex Beds) from 1993.

Marc Quinn (represented in Fleissig's collection by a drawing for his blood head work, self, once said of the "nvisible collection" that "to paraphrase Bruce Springsteen on Roy Orbison, contemporary art should look like it has dropped in from another planet but goes straight to the heart of how we live today", which is a pretty good summation of "Family".

Fleissig is unwavering in his support for the artists he likes regardless of changing fashions and revisionist thinking. "You can tell a lot about Peter from the nature of his collection," says Nesbitt. "I've met many collectors who'd rather be seen dead than lend works to a museum exhibition - let alone artists and friends; with Peter it's the other way round."

He will not want to read this and will dismiss it as irrelevant in this context, but he is held in great affection by many and they keenly support him - as he does them - and are effusive where he is reticent: "Peter was so determined," says gallery owner Sadie Cole, "that I should live in a particular street [in Notting Hill], that he persuaded his girlfriend Eve to lend me her flat, which he had helped design. I noticed, still in its original wrapping, a photograph by Gabriel Orozco. I mentioned it to Peter and the next day he showed up at my flat with it. It was an incredible present and I had it for six months."

Mark Pimlott, who lent a piece to the Kiev show - and ended up installing it ("the Ukrainian customs X-rayed these enormous suitcases and we agreed the collection never looked better") - admires "his combination of generosity, inquisitiveness and the ability to foresee affinities between people".

At this point I must declare my own hand: a few years ago, Peter had the first showing of the "nvisible museum", in a half-developed warehouse on the edge of the City of London. To be honest, having met Peter only once or twice I didn't really know what he was all about but it was on my way home ... I stayed for hours, enthralled in the semi-darkness by the most peculiar and eclectic assemblage of photographs, sculpture and painting. It was my introduction to a world of contemporary art that I knew nothing at all about. Most remarkable of all of them, for me, were the first photographs I had come across by Nobuyoshi Araki. Four years later you can't move in an arts bookshop without knocking over piles of monographs by this controversial artist and I am delighted to report that I am custodian, for the time being, of Araki's untitled silver gelatin prints. And I am the one person for whom Peter's ability to foresee affinities failed to produce the sparks he so likes to see. At an exhibition of Larry Clark's photographs, at the Karsten Shubert Gallery (home in those days to Rachel Whiteread, but now gone), he shooed me into Karsten Shubert's office and said "Karsten you really should meet the curator Robin Muir", to which Karsten replied blankly: "Why?"

`Family' Inverleith House, The Royal Botanic Gardens, Edinburgh December 13 1998 to January 31 1999

Peter Fleissig (on the left) with his friend James Lingwood of Artangel; art works from top, `Ideal Standard Forms' (1981), Edward Allington, courtesy Lisson Gallery; `Opposite Harmony No 45408 / No 100100' (1990), Tatsuo Miyajima; `Pharmacy Edition' (1994), Damien Hirst

This spread, clockwise from top: in foreground `A Model History' (1987), Mark Wallinger, pictured while on loan to Serpentine Gallery; `Jumping into the Void' (1960), Yves Klein ( Harry Schunk); `Dead Space' (1989) and, on floor, ` Pipes in a Basket' (1989), both by Cady Noland, courtesy Anthony Reynolds Gallery; `Untitled' (1988), Tansy Spinks; in foreground `Fort' (1989), Rachel Whiteread, pictured on loan to Hayward Gallery; `The Physical Impossibility of Death in the Mind of Someone Living' (1992-1994), Damien Hirst, courtesy White Cube; `Untitled', photographs (1990) by Araki Nobuyoshi; `The Emperor's New Pose' (1985-1986) by John Keane (Angela Flowers). All rights of work reserved with the artists