A new perspective: How Turner's famous views of Venice turned out to be paintings of Portsmouth

If only he'd written the title on the back, we wouldn't be having these problems. But admirers of JMW Turner might assume, a little optimistically it turns out, that the landscapist's swirling visions of browns, yellows and greys would be instantly identifiable.

As they were indeed identified - twice. First as images of perhaps the most romantic city in the world, then, it was revealed yesterday, as scenes of perhaps the most romantic city in Hampshire.

For two Turner paintings - Festive Lagoon Scene, Venice (1840-5) and Procession of Boats with Distant Smoke, Venice (1845) - might not depict the glorious Italian floating city at all but show instead Portsmouth, the dock city on the south coast of England.

The apparent error has been unearthed by Ian Warrell, a curator at the Tate Britain gallery, as part of his research for an exhibition on Turner and Venice at Tate Britain on 9 October until 11 January. The Tate owns thousands of Turner's works, which were bequeathed to the nation when he died in 1851.

As a result of Mr Warrell's discovery, the paintings have been renamedThe Arrival of Louis-Philippe at Portsmouth 8 October 1844 and The disembarkation of Louis-Philippe, 8 October 1844.

The works were wrongly classified in the 1960s when they were shown at the Museum of Modern Art in New York. They became grouped with other seemingly Venetian works by Turner in 1966 and that interpretation has gone unchallenged since.

Writing in the exhibition catalogue, Mr Warrell says: "Many of the details do not sustain the connection" with Venice. "A link with Venice, while plausible, possibly says more about the myths that continue to envelop the floating city [and a] desire to enshrine Turner as the prophet of abstraction."

He adds: "First, the size of the canvas is substantially larger than that used for the 19 small Venetian pictures that Turner exhibited between 1840 and 1846. This is an important point, for he imposed fairly rigid limitations on himself with regard to his materials when working in series."

No buildings are visible in the pictures, though there appears to be "a line of soldiers in red uniform standing patiently to attention". English troops, who wore red uniforms in the 19th century, would be, he remarks with understatement, "clearly an anomaly in a Venetian subject, but would not be so in one closer to home".

It is then that Mr Warrell goes for the kill: "A more appropriate identification of the pictures could, therefore, be the arrival of the French king, Louis-Philippe, at Portsmouth on 8 October 1844."

The theory makes a lot of sense. Letters from Turner show that he was in Portsmouth on the occasion, and a group of his studies have been related to the event.

Turner had known Louis-Philippe when the Duc d'Orlean's son lived in exile in Twickenham. In 1838, the king gave the painter a gold and diamond snuff box in exchange for a copy of his Picturesque Views in England and Wales.

Louis-Philippe came back to England in 1844, in order to reinforce his good relationship with Queen Victoria. She saw to it that his arrival by steamer was not a low-key affair, with gun salutes and big crowds at the quayside in Portsmouth. The Illustrated London News reported that "the whole population thronged the beach," watching as with every "moment this scene increased with interest". Other reporters noted the presence of troops, whose lines stretched "from the royal dockyard to the railroad terminus".

Mr Warrell writes that this was "presumably the same display of military decorum that impressed Turner".

The Turner paintings do not show Louis-Philippe's steamer, but they are believed to depict the flotilla that accompanied it.

A spokesman for Tate Britain said: "We certainly cannot be sure - one never can about such things - but we certainly feel that it is a very likely possibility that these paintings are of Portsmouth, not Venice as has previously been thought."

He added: "Venice and Portsmouth are, of course, very different places."

The art historian Tim Marlow, director of exhibitions at the White Cube gallery in London, who presented a BBC documentary on Turner last year, was excited by the revelation. "Bloody marvellous," he said when informed of the development. He paid tribute to the work of Mr Warrell. "This is just what great curators should be doing. And Ian Warrell is a great curator." He added: "If this were to happen to any great painter, it would most likely be Turner because he travelled so voraciously.

There is a further aspect too: Turner's abstractions have often led to debates over their interpretation. Though often described as Britain's greatest landscape painter, he was ridiculed in his lifetime, particularly towards the end of his career, when the fashion was for realism. Queen Victoria is said to have considered him mad; famously Turner's Snowstorm was said to look as if it had been painted with "cream, chocolate, eggs and jelly" and dismissed as "soap suds and whitewash".

Such an abstract style has led to confusion before. Eric Shanes, a painter and Turner expert, reattributed a work by the artist in 1984. "I realised that a painting that for more than 100 years had been known as a view of Monte Rosa in Italy was in fact Inverary Pier in Scotland," he said. He made the reidentification when he was looking at a series of Turner prints, called Liber Studiorum, from the late 1800s and 1810s, with a book of later oil paintings open alongside. One of the prints was clearly identified as being of Inverary pier and he could see the clear connection between it and one of the oil paintings from around 1845 which had been previously described as of Monte Rosa.

Similarly, about three years ago, he helped to provide the correct titles for five watercolours from Turner's first trip to Switzerland in 1802. "The titles had got totally mixed up and with the titles had come wrong dates. "Once somebody has made a misidentification with these late Turners everybody just follows like sheep because there's so little to go on in the way of topography and so on. Visually, these late works are loose and filled with light and colour and so it's very easy to make mistakes."

The two Turner works will not be withdrawn from the Tate's exhibition, despite its subject matter. So will the show be renamed "Turner and Venice and Hampshire"? The Tate spokesman does not pause for breath. "No."

HOW VENICE AND PORTSMOUTH COMPARE

VENICE

Famous for: Romantic canals and beautiful mosaic-clad palazzos dating from the 12th century to the 18th.

Wish you were here? The Lonely Planet guidebook says: "From the sensuality of Veneto-Byzantine to the extremes of Baroque, the concentration of architectural gems is astonishing."

Artistic impression: Titian, Tintoretto and Canaletto based themselves in Venice. El Greco studied there. Vivaldi was a Venetian as was Casanova. Of Venice, Shelley wrote "Underneath Day's azure eyes/Ocean's nursling, Venice, lies."

Roll up, roll up: Every year, 17 million tourists visit Venice. The Veneto region makes up 13 per cent of all Italy's tourist revenue.

Waterworks: There are 268 square miles of waterways, mostly working canals, including the magnificent Grand Canal.

PORTSMOUTH

Famous for: The Historic Dockyards, which contain HMS Victory, Admiral Nelson's flagship at the Battle of Trafalgar, and the remains of the Mary Rose.

Wish you were here? The Lonely Planet guidebook says: "Unfortunately, Portsmouth is not a particularly attractive city, largely due to Second World War bombing." Population: 190,000

Artistic Impression: Rudyard Kipling lived in Portsmouth for a while; Dickens was born there. Both moved away. Arnold Schwarzenegger trained at a gym in Southsea.

Roll up, roll up: The Historic Dockyards, the top Portsmouth tourist attraction, attracted 422,000 visitors last year.

Waterworks: There are no working waterways. The Portsmouth and Arundel canal closed in 1906.