It may be bonnie, but it's not Prince Charlie, embarrassed art gallery chiefs discover

A PORTRAIT of Bonnie Prince Charlie, by the French master Maurice-Quentin La Tour, has hung with pride in the Scottish National Portrait Gallery since it was snapped up in 1994.

But the pastel portrait of Prince Charles Edward Stuart is actually of his younger brother Henry, a London art researcher has concluded.

Last night, the gallery's former director, Dr Duncan Thomson, who oversaw the purchase of the work, admitted it was probably a portrait of Henry, a cardinal.

"It's become an awfully important image of Bonnie Prince Charlie. I think I have got to confess guilt in this instance," he said. The British Art Journal, the leading art research publication in Britain, published the new account of the picture.

"There is no doubt at all about it," said the editor, Robin Simon. "It's rare that anything is so spectacularly wrong."

The 5ft-tall pastel of the man in armour was bought at auction by the gallery for £22,000 as a portrait of Bonnie Prince Charlie. Its earlier history was unclear yesterday. It came to be seen as a classic image of the prince and was used as the cover for an edition of Fitzroy Maclean's classic biography of him.

Prince Charles Edward Stuart, also known as the Young Pretender, was the elder son of the "Old Pretender", James Edward Stuart, and the grandson of James II and VII. He fled into exile after his forces were defeated at Culloden.

Prince Henry Benedict, his brother, was born five years after Charles in 1725. He was known as the Duke of York or Cardinal York until his brother's death in 1788, when he claimed the title of Henry IX.

But earlier this year, a painting called Portrait of a Cardinal was auctioned in London from the collection of St Mary's Roman Catholic College, Twickenham. It was bought by London dealers Philip Mould. After cleaning and research, and comparing it to other pictures, it was identified as a lost portrait of Henry.

Bendor Grosvenor, a director of the firm, became convinced it was a copy of the portrait gallery's pastel.

"It was a dead ringer. He compared the details of his portrait of a cardinal with this La Tour pastel. It was a brilliant thing to have done," said Mr Simon.

So how then did the La Tour pastel in the portrait gallery became identified as the prince?

"You can see how it happened. People got muddled over who sat for this wonderful painter, La Tour, and missed the rather important point that Cardinal Henry had also sat for La Tour," said Mr Simon. "They thought it was only Bonnie Prince Charlie that sat for him in 1747."

One thing that fooled experts into thinking it was Charlie is the sitter's armour. But it is thought the picture was done before Henry became a cardinal. "They expected a cardinal to dress like a cardinal, not like a martial arts expert," he said.

No-one from the National Galleries of Scotland was available for comment last night.

The consolation prize for the gallery is that it still has a La Tour portrait. The picture is potentially worth hundreds of thousands of pounds or more, though it is perhaps less valuable than a portrait of the prince. The re-identification will not affect its standing as a work of art.

Another mystery is the whereabouts of La Tour's portrait of the prince, if it still exists.

Dr Thomson said: "I take it very seriously."

He added: "There's so much circumstantial evidence. It looks like Henry Benedict, I've got to confess.

"I was fooled by the fact he is wearing armour, which is what soldiers did, and cardinals don't wear armour.

"But in fact Henry Benedict had briefly been technically a soldier."

Beware the masterpiece that's a pig in a poke

ONE of Scotland's most famous paintings, Reverend Walker Skating on Duddingston Loch, has been the subject of a similar controversy.

For centuries attributed to Sir Henry Raeburn, in 2005 a senior curator at the National Portrait Gallery cast doubt on whether it was painted by Raeburn. The debate continues today.

A swathe of Jackson Pollock's dripped canvases have also been at the centre of serious academic scrutiny. His famous No5 piece, which was sold for £73million in 2006, was branded as a fake by some academics even as it went on sale.

And a collection of 32 recently discovered canvases attributed to the abstract expressionist are the subject of continued controversy.

Even contemporary artists are not immune. Grayson Perry, the cross-dressing Turner Prize-winning potter, has fallen victim to forgers.

An embarrassed Christie's has been forced to withdraw a glazed ceramic sculpture of a boar from auction tomorrow, after the artist told them that he had not made it.

Perry said it had to be a fake because it was too well made to be one of his early works.

The piece has been reattributed as "English school", reduced in value and returned to the seller.