Today brings a small commemoration in an Oxford suburb. It is the 21st birthday of the Headington Shark: a 25ft-long fibreglass sculpture representing, with startling realism, the body and tail of a large shark, apparently having dived out of the sky to crash through the roof of a Victorian terrace. The house belongs to Bill Heine, now an eccentric local radio presenter, who commissioned it from the sculptor John Buckley.

A crane lowered the shark into position on August 9, 1986. It was the anniversary of Nagasaki and shortly after the US bombing of Tripoli; Heine said it was a comment on war: “Saying something about CND, nuclear power, Chernobyl and Nagasaki”. Buckley tells me more modestly that he just liked doing tiger sharks, and enjoyed the idea of expressing the fragility of “plaster and tiles . . . all that protects the Englishman’s castle”. He was also glad to get something done; he had spent three years “trying to put another sculpture up in the right way. Sponsorship, permissions, it all folded.”

Heine didn’t bother with “the proper way” and asked no permissions. There was uproar . The local council at first said that the shark was a danger to public safety, but then its engineers reported that the supporting girders were fine, despite the great height of the shark above the rooftops and its considerable weight. “It’s a good aerodynamic shape,” says Buckley proudly. “It withstood the ’87 hurricane, when some houses got their roofs blown off.” The council then announced that it was a prohibited development under Section 22 of the Town and Country Planning Act 1971 and must be removed. The council offered to erect it at the local swimming baths. Heine preferred it on his roof. In 1990 permission was refused; he promptly appealed to the Secretary of State for the Environment – Michael Heseltine – whose inspector, Peter Macdonald, ruled in his favour.

In a wonderful statement Mr Macdonald said that while the shark was not in harmony with its surroundings, it was not meant to be; the contrast was deliberate, essential to its meaning. Moreover, “an incongruous object can become accepted as a landmark after a time, becoming well known, even well loved in the process. . . I cannot believe that the purpose of planning control is to enforce a boring and mediocre uniformity. Any system of control must make some small place for the dynamic, the unexpected, the downright quirky.” The chairman of the local council’s planning committee was quoted as saying, enragedly, that the decision was “a slap in the face of decent and respectable people”.

In this very spot in The Times, the late Bernard Levin uttered a paean of support for artist, patron and planning inspector. He called as witnesses Shakespeare, Acton, Hazlitt and Heinrich Heine (no relation). Without bothering with the war message he praised the sculpture itself – “delightful, innocent, fresh and amusing”. Above all, Levin rejoiced at the inspector’s defence of liberty and eccentricity against “fun-killers, the pursed lips brigade . . . Anyone but a prize nana would have seen that Mr Heine’s splendid lark was an exact definition of delight, particularly Shakespeare’s kind ‘that give delight and hurt not’.”

Well, God rest Levin and happy birthday to the Headington Shark. But another moral comes to me 21 years on: sculptors envisioning public works hold a unique and important position yet suffer more frustration, probably, than any other creative artists. A painter, writer or solo composer may complete a vision and perfect it, whether or not anyone likes it enough to buy it. At least it exists. A sculptor – like a composer of symphonies or a dramatist – must win the cooperation of others. Before the piece can be truly born, finding its proper scale and setting, there must be funding and permission and the faith of those with power. And the powerful may be timid, nervous, or so in thrall to fashion that they demand trendy names and dismiss lesser-known ones.

Even then the work may meet public contumely. Yet it is one of the joys of public sculpture that we get used to it: those who would never voluntarily go into an art gallery walk past every day and over years grow fond of it. Thus, however grudgingly, the mass of us enter into the vision of the artist and are almost imperceptibly enlarged and enriched by that unsought communication. I never “got” Barbara Hepworth until, week after week, my children played around her Family of Man at Snape Maltings in Suffolk; Maggi Hambling’s scallop shell at Aldeburgh is winning many who at first shuddered (not all, but give it time). It has taken me nearly a decade to warm to The Angel of the North, but I’m getting there.

So I asked Buckley what he is doing now. And as it happens, last week another long attrition ended in success and a project close to his heart was confirmed. We are two years into the United Nations’ Decade for Action – Water for Life. Buckley has travelled repeatedly to the Nuba mountains in central Sudan, where tribal people dig in the dry riverbeds to find the water table. He walked with their women “for seven hours at a time in 45-degree heat, to fetch 20 litres of water” and created a sculpture of two Nuba girls watering young plants.

Now it is to be cast in bronze for the Centre for Ecology and Hydrology at Wallingford, in Oxfordshire. And those who hurry past it, to their researches on worldwide flood and drought, will be reminded of the human dimension, the battles and hopes of unremembered individuals. Less of a lark than the shark; but once again, worth doing. And those who put their visions out there for us, the sculptors, are worth saluting.

Read Libby Purves’s blog about God, faith and grumpy atheists

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