It began with the boiling of waters, 22 miles from the island of fire. It was July 1861, and off the coast of southern Sicily – the fiery island of volcanoes – in the Sicilian Channel between Europe and Africa, strange things were happening. There was a terrible smell of sulphur in the air, and jets of hot water and cinders were spat from the ocean. Dead fish floated on the surface. Commander Charles Henry Swinburne, standing on the British naval frigate HMS Rapid, watched as for only the second time since 10BC, one of Sicily's lesser-known volcanoes rose up from the sea, setting off an international dispute between Britain and Italy that is still, theoretically, unresolved.
The British returned in August 1831, claiming the now sizeable hillock as Graham Island, after the First Lord of the Admiralty, and gleeful at grabbing such a strategic lump of rock: closer to Europe than Malta, Graham Island was a perfect point to control commercial and military sea traffic in the major Mediterranean shipping lanes. The Sicilians – Italy wouldn't be unified until 1870 – indignantly sent a ship to claim the island for the Bourbon Kingdom of the Two Sicilies, whose captain removed the Union Jack and named the island Ferdinandea, after King Ferdinand II. The Spanish showed an interest too, while the French sent a geologist to name it Giulia, on the prosaic grounds that it had appeared in the month of July.
For five months, conflict raged in newspapers, as three nations fought over a 60m-high lump of basalt. Tourists travelled to the island to see its two small lakes and four-kilometre circumference; hardy visitors climbed to its summit through clouds of noxious gas. Sailors watched with suspicion, muttering of magic forces that must make the island pop up and down, while the nobles of the House of Bourbon reportedly planned to set up a top-class holiday resort on its beaches. But it was no use. Little by little, the island sank back beneath the waters, and by 17 December 1831, two Neapolitan officials reported no trace of it. The volcano had been drawn back down into the sea by the movement of the tectonic plates, the same way it had arisen, and the dispute was seemingly resolved – no territory, no territorial claim.
Until now. The seamount (a seabed volcano) of Graham/Ferdinandea has lived on in charts, its summit – only eight metres below the surface – a constant hazard for shipping. Occasionally it has made its presence known, alarming fishermen with its steaming. In 1987, an American pilot on the way to bomb Libya thought the rock a submarine, and dropped depth charges on it. In 1995, tremors along the Sicilian coast were blamed on Ferdinandea. Then last year, the squabble over a non-existent island spluttered once more into life.
Domenico Macaluso is a surgeon in Sciacca, the coastal town nearest to Ferdinandea, as he calls it ("You'll be wanting to call it Graham, I suppose," he says on the phone). A keen diver, and a volunteer Inspector of Sicilian Cultural Riches, he was horrified by the underwater foraging of the famed American diver Robert Ballard, who had been poking around in the Sicilian Channel and began to take an interest in Ferdinandea. Macaluso's interest intensified last year. "It was 5 February 2000," he states with obsessive precision, when a bout of volcanic activity prompted a newspaper article entitled "A long vanished piece of the British Empire is about to resurface". This caused "a certain embarrassment in certain quarters", says Macaluso, including in the Italian Ministry of Foreign Affairs. Anxiety pricked by rumours that two British navy ships had been sniffing around the area, possibly checking out the truth of the press story, the Italian government asked for a report on the situation from its voluntary cultural inspector.
There was no chance of Ferdinandea re-emerging any time soon, the report concluded, but that didn't mean it wouldn't, one day. After all, the British had never made a formal claim to Graham, beyond sticking a flag on it. Ferdinand II had gone further, declaring with an Act of Annexation that Ferdinandea belonged to the Kingdom of Two Sicilies. But under international maritime law, Ferdinandea/Graham lies just outside Italy's 12-mile territorial waters. In theory, anyone – from Libya opposite, to nostalgic imperialists in the British fleet, to the House of Bourbon – could claim it, and the waters between Africa and Europe are as strategic now as in 1831.
Macaluso decided to take action. "I'm not political," he stresses, but he is determined. He persuaded Ferdinand's descendant, Prince Carlos of Calabria, who'd never set foot in Sicily, to take part in a "cultural initiative", in the form of a 150kg marble plaque, inscribed with the coats of arms of the House of Bourbon, the Italian Navy and the town of Sciacca, and with the words: "This piece of land, once Ferdinandea, was and shall always belong to the Sicilian people." It was all done in the name of the long-dead Ferdinand of Bourbon, Duke of Castro, and placed 20m below the surface in March this year, an event commemorated by the Italian media. The publicity brought curious tourists back to this anonymous patch of sea where there was nothing to see.
It brought someone else, too, because when Macaluso dived down to the island four weeks ago, he found his beloved plaque in pieces. Twelve pieces, actually, apparently bearing the marks of severe blows. He cried foul. "It's vandalism!" Italian newspapers, remembering the G8 protests in Genoa, speculated about a "Black Bloc" of underwater anarchists. More sober observers pointed to fishing anchors, accidental damage, maybe an earthquake, but Macaluso is unconvinced. "It was a considerable undertaking, to dive down there. If it had been an anchor, it would have broken in two, not 12 pieces. It was deliberate." Could it have been the dastardly British? "I don't think they could be bothered to get in a sub and go and break a piece of marble. Maybe it was someone with a grudge against the Bourbons."
Filippo D'Arpa, a journalist with Il Giornale di Sicilia, pours cold water on any conspiracy theories. His novel on the events of 1831 – The Island That Went Away – published this month in Italy, is "a metaphor on the ridiculousness of power. This rock is worth nothing, it's no use as a territorial possession, and yet the English, the French and the Bourbons fought over it and nearly came to war". Even so, "even now there's a strong rivalry, because the ownership of the island has never been established. It's very peculiar that 160 years later, English and Italians are still fighting over this."
Not so, says the Foreign Office spokeswoman, who downplays any claim, but knew exactly where Graham Island was. She asks briskly whether a quote she gave Time magazine would be OK. "I think we said we weren't going to make waves about it, or something humorous. It's that kind of level."
But it pays to take small islands seriously, however insignificant they seem. Three miles off Southend-on-Sea, Roy and Joan Bates have defied Her Majesty's Government for 30 years to claim sovereignty for their principality of Sealand (actually a concrete gun fort).
Japan's 200-mile exclusive economic zone uses a boundary marked by humble crops of coral surrounded by concrete. And in the book Lost Islands the oceanographer Henry Stommel listed many more undiscovered islands – marked on charts, but missing – which could be claimed for offshore banking services, principalities or radio stations, if anyone could find them.
"It's a very thorny issue," says Martin Pratt of the University of Durham's International Boundaries Research Unit. "You can't have sovereignty without territory, and you usually need some kind of continuous possession. But theoretically, if it did emerge again, it's outside Italian territorial waters, and someone could possess it and claim it."
An Italian naval captain recently wrote an article about Ferdinandea entitled "A Virtual Dispute". But a dispute it still is. Enough for Macaluso to be invited to Brussels to discuss the situation at official level, and for the Belgian newspaper Le Soir to put the story in full-colour on its front page. Enough for physicist Antonio Zichichi, who keeps an eye on the volcano from the Ettore Majorano Centre at Erice, to say immediately, "We're not interested in any plaques!" Zichichi heads a project "to understand what's going on in that part of the sea", including correlations between Ferdinandea's activity and seismic shocks on Sicily's southern coast. "I intervened because people were saying such stupid things about Ferdinandea – that it was magic, that it was going to erupt. It goes up and down because the earth's crust goes up and down, and that's that." But a Nato report last year about a similar seamount off northern Sicily speculated that a new emergence could cause huge tidal waves. And even Zichichi, a strong believer in Galileo's dictum that our lives must be governed by facts, admits that for now, Ferdinandea hasn't supplied many. "People should have started monitoring 20 years ago, not five," he says. "It's a very difficult task – in the advanced frontiers of geophysics, it's impossible to predict seismic events."
And as long as the possibility that the non-existent island will exist again cannot be ruled out, the virtual dispute can rumble on. So Macaluso is determined to replace the plaque. The tourists will continue to circle over a volcano eight metres underwater. In government offices, files will build up on the what-ifs. And meanwhile, the volcano called Ferdinandea or Graham bubbles away, causing eruptions and waves in the realm of hypothesis, while its mineral sands sprout with lush underwater plants. The aristocratic beach resort is now a haven for fish and 40 varieties of microsnails. Coral has begun to form. "It's an underwater paradise," says Macaluso. "I'd prefer it to stay down there. It's better that way, for everybody."