The art dealer Nigel Greenwood never achieved the renown of his near-contemporaries Robert Fraser and John Kasmin. Fraser and Kasmin, who had the support of wealthy backers, a luxury that Greenwood never enjoyed, allied themselves with the second wave of British Pop artists in the early sixties and quickly found themselves bathed in the same kind of media glamour which attached itself to Patrick Caulfield, Bridget Riley, Derek Boshier and David Hockney, an artist who ascended to previously unimagined heights of fame shared only by pop stars such as the Rolling Stones and the Beatles.

Greenwood was closer in age to Hockney and his contemporaries than to the fashionable dealers who represented them. But, in art terms, he was temperamentally out of sympathy with the brasher forms of popular culture from which Pop emerged and which it, in turn, bled back into. Pop art was about ‘liking things’, as its avatar Andy Warhol once said. It was about surface appearance – the resounding shallows of consumer culture; the complex sheen of advertising and packaging; it was about everything bright and synthetic and American. The American Pop artists in particular were not much interested in ideas.

Nigel Greenwood’s was a cooler, cleaner, more rigorous and more cerebral, even monkish, aesthetic. He was stimulated by ideas and instinctively drawn to the ‘idea art’ – minimalism, conceptualism, installation, performance, and site-specific art – which he started to show at his Chelsea gallery in London from around 1970. In the commercial sector, Greenwood stood bravely alone at that time in fostering the climate for difficult, advanced art in Britain. It was rewarding but not remunerative.The Saatchi era of getting and spending, of ‘I want it all and I want it now’, was many years in the future.There were perhaps two serious collectors of new art in the whole country. It was an uphill struggle. To his immense credit, Greenwood never bent with the winds of fashion; he never compromised and never wavered in his commitment to work which was frequently intractable and occasionally even virtually invisible.

Conceptualism was famously about the ‘withdrawal of visuality’, and visitors to the Nigel Greenwood Gallery were sometimes unclear about what it was they were meant to be seeing. But the ‘gallerist’ (a term not invented in those days) was always discreetly on hand to point out the quiet interventions of a David Tremlett or a Richard Tuttle, or the almost imperceptible inflections in a grey monochrome Alan Charlton painting. Shows such as the grids of austere black and white photographs of pit-head winding gear and industrial cooling towers taken by the German husband-and-wife team Bernd and Hilla Becher, then unknowns, now stars of the international art firmament, were either ignored or routinely rubbished by the critics.

‘I’m just used to everyone bitching about everyone,’ Greenwood once said, ‘treating you like an old doormat over which they want to walk. They’ve made their mind up in advance. Generosity is not a quality for which the British art world is renowned. Britain manages to sell itself on negativity. If I was on Broadway, I’d have to close every show immediately. Thank God one isn’t entirely dependent on the idiosyncrasies of the English press.’ Greenwood had an infectious, instantly recognisable laugh and it was frequently to be heard echoing around the tall, elegant rooms of the gallery off Sloane Square.

Nigel Greenwood was born in Plymouth and grew up in the village of Noss Mayo in South Devon. He attended a prep school in Elstree, Herts, and then Sherborne School in Dorset, which he hated. He went to Christchurch, Oxford, but left after a year for a spell in Rome, during which, when he wasn’t teaching geography and Latin at St George’s English School, he was earning pocket money as a background extra in the Burton–Taylor Cleopatra and Visconti’s The Leopard.

He was a student of Anthony Blunt’s and John Golding’s at the Courtauld Institute in London from 1962 to 1965 and was then taken on as manager of the Axiom Gallery in Duke Street, a few doors from where, two years earlier, Robert Fraser had opened what soon became the most fashionable gallery showing contemporary art in Europe. Kasmin was nearby, and between them they formed a key axis of a London whose new mood the poet Christopher Logue described in his autobiography as ‘friendly, self-centred, improvisatory, carefree, and frivolous’:‘Sexiness was flaunted and prized.There was a hint of freebooting, of danger . . . An act of will was evident: this party is going to last.’

It was a party at which Nigel Greenwood, ascetic only in his taste in art, was a welcome and enthusiastic guest. When he held his first exhibition, at a studio in Glebe Place in Chelsea in 1969, it was in a building where the Beatles had posed for the 1967 cover of Sgt Pepper and where the album’s photographer, Michael Cooper, was still a neighbour.

In 1971 he found the space, further down the King’s Road, that he would turn into London’s least parochial, most independent-minded gallery and his home for the next thirty-three years. Downstairs I could make storage for the art and myself with even a spare room for visiting artists,’ Greenwood recalled recently.‘Once the doors and radiators were removed and a coat of white paint covered all the walls, part of this unremarkable Chelsea house was ready to sail into the uncharted waters of the seventies avant-garde with what was to prove a riotously diverse crew.’

Within a few months of opening he had discovered the gallery’s first art stars in the ‘living sculptures’, Gilbert and George. Reclining Drunk was a display of 200 Gordon’s Gin bottles flattened as ashtrays and arranged on the gallery floor. Underneath the Arches featured the artists miming for hours to the old Flanagan and Allen song, standing on a canteen table. In 1974, Greenwood published Dark Shadow, a beautifully hand-finished book version of Gilbert and George’s ‘drinking sculptures’, many of which had been rehearsed on a now folkloric tour to the Far East and Australia in the company of the dealer the year before.

Greenwood’s involvement with artists’ books continued as an integral part of the activities of the gallery.When he eventually bowed to the inevitable and transferred his business to the West End in 1985 (‘some of the artists wanted the surroundings of success’), Nigel Greenwood Books expanded to sell books and catalogues to libraries and collectors all over the world, as well as publish a book list of 200 current titles three times a year.

He continued to work as an adviser and private dealer after the gallery was forced to close in 1992, but there was a sense that his huge reserves of knowledge and experience, as well as an undiminished passion for art and a rare talent for making and sustaining friendships, were senselessly underused by a public sector which would have done well to harness them.

After his cancer was diagnosed, he showed an unsettling awareness of the scandal of death, and its finality. But he continued to talk about art and artists, pumping friends for news of shows they had seen, to the end. The Donald Judd retrospective at Tate Modern was one of the last exhibitions he visited and he reported that he found its plainness and authority – its puritan spirituality – comforting. It made him feel alive.

Nigel Greenwood, art dealer, was born on 28 May 1941. He died on 14 April 2004, aged sixty-two.