The portrait by Maurice Quentin de La Tour has become an iconic image
The National Galleries of Scotland has conceded its portrait of Bonnie Prince Charlie is probably actually of his younger brother Henry.
The painting, by Maurice Quentin de La Tour, has hung in the Scottish National Portrait Gallery since it was bought for £22,000 in 1994.
Now a leading expert believes the pastel might be Prince Henry Benedict instead of Charles Edward Stuart.
The gallery said it was not uncommon for re-attributions to be made.
It follows a two-year row over the identity of the man in the painting since London art dealer Bendor Grosvenor claimed it was not Bonnie Prince Charlie.
At first the gallery dismissed the claim citing expert on Jacobite portraiture, Dr Edward Corp of the University of Toulouse, France, in its defence.
However, Dr Corp has now changed his opinion in an article in the latest issue of The British Art Journal.
He said: "'The weight of evidence, perhaps regrettably, supports Bendor Grosvenor's argument that the pastel in the Scottish National Portrait Gallery shows Prince Henry rather than Prince Charles."
He added: "'Whether the portrait does or does not show Prince Charles really does matter.
"It is not merely the catalogue of the Scottish National Portrait Gallery which needs to be corrected.
"The impression which an entire nation has derived of this important historical figure should also be changed.
"The portrait is now reproduced in all biographies of the prince, and has been selected to illustrate the article about him in the Oxford Dictionary of National Biography."
A scent bottle, 1753, showing the lost portrait of Prince Charles Stuart
A National Galleries of Scotland: "In the light of this development, we have re-assessed our own position and, on balance, accept that it is more likely that our pastel depicts Prince Henry Benedict, and not his elder brother.
"It is not uncommon that such re-attributions are made, as research continues to fill in gaps in our knowledge, and it is always exciting to uncover new information about the works in our care.
"None of these debates detract from the greatness of the portrait.
"As an image it still projects the glamour of the Stuart cause, it is simply that we must readjust to seeing Henry, always rather in the shadow of his brother, in this role, rather than Charles."
A description about the controversy surrounding the picture will be attached when it goes back on show at the gallery in two years' time following a revamp of the building.