He is one of Britain's greatest painters, a visionary whose depictions of landscapes marked him as among the nation's finest artists.

But Joseph Mallord William (JMW) Turner, renowned for such paintings as The Fighting Temeraire and Rain, Steam and Speed, also created his own distinct vision of mythic Scotland, "lost" for decades and now rediscovered by an academic.

The landscape of the Loch Lomond area by Turner, who lived from 1775 to 1851, has been billed for many years as a Welsh landscape in the collections of the prestigious Fitzwilliam Museum of Cambridge University.

However, artistic detective work by Professor Murdo Mac­donald, of Dundee University, and Eric Shanes, a former chairman of the Turner Society, has proved it is a landscape of Scotland, depicting one of the most successful but controversial fables of Scottish history.

The Welsh landscape is, in fact, a work of Turner's from 1802, entitled The Traveller - Vide Ossian's War of Caros, say Mr Macdonald, professor of history of Scottish art at Dundee University, and Mr Shanes, now a vice-president of the Turner Society.

They also believe the figures in the painting, bought for the museum in 1925, are characters from the writings of Scots poet James Macpherson, whose apparent discovery of the works of an ancient Gaelic bard, Ossian, caused a literary sensation in the late-18th and early-19th centuries.

Turner was clearly inspired by the often gloomy and violent tales, and painted the scene after his first visit to the Highlands in 1801.

Mr Macdonald and Mr Shanes, using maps and scouting of the Scottish landscape, pinpointed exactly where Turner set his mythic vision: Rubha Mor, six miles to the south of Inveruglas.

He also found a drawing by Turner in the Tate Gallery, showing a view of Loch Lomond, the "clear basis of the painting".

He said: "The Ben Lomond work becomes a pivot between Turner's seascapes and his ­imaginary landscapes.

"So, for the first time since the title and painting became detached from one another, it is possible to appreciate fully the psychological balance of Turner's first exhibits in oils at the Royal Academy."

He added: "The painting is significant in another sense. It seems to be Turner's first response in oil paint to poetry based on a landscape he had himself seen, and that is, of course, one of the defining themes of his career as a whole."

In 1802 Turner exhibited eight works at the Royal Academy in London and one of them was exhibit '862, Ben Lomond Mountains, Scotland: The Traveller -Vide Ossian's War of Caros.

However, when catalogued in the 1970s, the painting was titled as a Welsh Mountain Landscape, and previously it had been titled In the Trossachs and dated incorrectly.

Turner's literary source, Ossian's War of Caros, was first published in 1762 in six books and he owned a copy of The Poems of Ossian in a 1797 edition.

In the story of the war of Caros, Hidallan, a dismissed general, visits his father, Lamor. In shame at his dismissal, Lamor kills his son and then himself.

Mr Macdonald said: "The seated man in Turner's painting is undoubtedly Lamor, holding his glinting sword and with a semi-circular form to the left of him that surely represents his discarded shield. At his feet lies the body of his slain son."

In his paper, he added: "Turner habitually imbued his landscapes and seascapes with feeling but in the general gloom that occupies the forefront of Ben Lomond Mountains, Scotland: The Traveller - Vide Ossian's War of Caros, he may have hinted at the darkness that has replaced Lamor's sight."

The article on the painting by Mr Macdonald and Mr Shanes is in the October 2013 issue of Turner Society News.

The Fitzwilliam Museum is aware of the research by Mr Macdonald and Mr Shanes but declined comment.