
Complete uplift: that is one way to describe Rose Finn-Kelcey’s most enduring work, a photograph of the artist performing a perfect handstand on a beach. It is a jubilant scene, immediately stirring the same impulse in the viewer. And yet it is also mysterious, for the pleated skirt she wears seems to fall upwards, covering her torso and head like a vast paper fan so that her identity is concealed. An image of exhilarating spontaneity turns out to emerge from close deliberation: that is one revelation of this enthralling survey.
Finn-Kelcey (1945-2014) needs and deserves a lifetime retrospective. She was an artist of evergreen originality. But though she came from a celebrated generation of conceptualists, from Susan Hiller to Richard Long, and although she taught a generation of equally famous YBAs, she was impressively leery of limelight and the gallery system. Her art, moreover, is frequently ephemeral and so unpredictable that no two works are ever alike. She avoided the signature look and the market commodity.
At Oxford, for instance, three exquisite yet mordant papercuts of suspicious figures – including Gaddafi, it seems, crawling into his hole – hang next to an LED sign flashing up ever more preposterous instructions in perfect parody of the nanny state. A classic doghouse hangs upside down from the ceiling, newly estranged like some kind of inverted tabernacle (God Kennel is its title). And a sequence of photographs shows a boxing glove impotently punching at a bubble, which simply floats free of these dumb blows. The vision is both moral and political in a gracious, undogmatic way, which seems to have been very much Finn-Kelcey’s style.
She came to public prominence in the 1970s with a series of colossal flags flown over London landmarks. Here Is a Gale Warning blew over the BBC’s Alexandra Palace, causing anxious citizens to phone into the news. Power for the People involved four enormous black banners flying from the corners of Battersea power station during a period of industrial unrest. Photographs of this dramatic intervention are startling enough, even today; the actual sight must have stopped passing traffic.

This subversion was not accomplished without great difficulty, and Finn-Kelcey wrote a vivid and hilarious account of the bureaucratic negotiations, which involved endless GLC red tape (including “one official lunch, complete with gin and tonic”). But absurd loopholes eventually allowed her to persuade a rigger to hoist the banners for a day. Whereupon she received official warning that what she had already achieved was, of course, strictly forbidden.
Her aim was for “a public art form that is neither pompous, interfering nor condescending”. That philosophy is embodied through this show. Pondering the oppressive hardness of modern architecture, she came up with a “room” entirely composed of steam, kept in place by curtains of air and spectacular to those who saw it. Contemplating God, she wrote to priests in Rome asking them to draw what they thought He looked like. The results are riveting: abstract, numinous, a pair of hands cradling a figure, flames, lights, hearts, a vast presence over which people clamber like so many children in a playground.

As a counter, Finn-Kelcey designed a chocolate machine that offers prayers for a refundable 20p, drawing analogies between the brand names – Bounty, Delight, Ripple – and the intense self-indulgence of the 21st century.
She could be fiercely epigrammatic. In the opening gallery at Modern Art Oxford, the curators have recreated Bureau de Change, from 1987, the year in which Van Gogh’s Sunflowers sold for a record $39.9m. Finn-Kelcey reprised this masterpiece in coins on the floor of Matt’s Gallery in London. Old money, new money, filthy lucre: the result is a strange, shining ghost of the original painting that turns it, literally, into hard cash. A museum guard patrols the scene so that nobody takes any of the artwork’s value, as it were, away.
Some of her work only exists now in photographic record – her famous performance with two magpies, for instance, in which the birds respond with wild variety to her curious attentions. But this show includes a film of Glory, a war enacted using shadow puppets at the Serpentine Gallery in 1983. The puppets are magnificently made out of paper – medieval jousters, cowboys, soldiers, nuclear blasts represented as comedy explosions: ignorant armies clashing by night. It’s some time before you realise that the puppeteer in the darkness is Finn-Kelcey herself, modestly edging out.

The Restless Image, as the handstand photograph is called, has a telling subtitle: a discrepancy between the felt position and the seen position. This should give any viewer pause for thought. And it turns out that much of her work is about this inner/outer disparity, which is, after all, the condition of every human existence.
Some of her lightest and wittiest pieces centre on herself, such as the little sponge into which she might squeeze her own exasperating ego. But sharpest of all is Book and Pillow. The eponymous book lies open on the pillow, but caught within its transparent pages, like the proverbial fly in amber, is a strange little being. The artist had imagined the most anxious and unimpressive side of herself and described it to a model-maker, who produced this tiny scarlet homunculus. Intrigued, you take up the magnifying glass hanging on the wall to examine this critter and find your head on the pillow, which activates a sound – the infuriating buzz of a fly.
• At Modern Art Oxford until 15 October