Painting was once part of royal collection

The painting, A Concert, was originally thought to be a Titian, but is in fact by an imitator.

Now investigations carried out by Nicholas Penny, the new director of the National Gallery, reveal it used to hang in the collection of King Charles I.

His research also confirmed that a dirty painting long thought to be a copy of a work by Italian master Paolo Veronese is the real thing.

The Rape Of Europa now hangs in the gallery's main collection as a result of the reattribution.

Dr Penny's research, which began in 1993 when he first worked for the National, is published today in a new £75 catalogue of 16th-century Venetian paintings.

The catalogue also reveals the histories of other key works.

The Family Of Darius Before Alexander by Veronese was purchased in the 1850s against competition-from the emperors of France and Russia.

"It shows the National Gallery at its most aggressive," said Dr Penny. "There has never been a period since when we've been buying in this way in the international art market."

The catalogue also reveals mistakes, including how one former trustee, Alfred Rothschild, blocked the gallery buying several important masterpieces. The director said this type of scholarship was at the heart of the gallery's work.

Dr Penny, 58, who has rejoined the National after seven years at the National Gallery of Art in Washington, said it does not enjoy the same government confidence as its equivalent in America.

He claimed much time and energy was devoted in Britain to showing they were doing the "right things". By contrast, his last employer was not scrutinised to the same degree.

This was part ly because it depended less on the government for funding. "A difference between this country and America is the tax incentives available to giving in various ways to the national institutions," said Dr Penny.

Britain had failed to court collectors in the way US galleries did so they lent - and eventually bequeathed - art to the major galleries. It should be possible to find and develop new collectors of Old Masters in Britain alongside the new generation of contemporary art buyers.

"Part of the National Gallery's job is to generate interest in Old Masters," said Dr Penny.