A painting donated to Britain’s National Trust in 2010 has been identified as a self-portrait by Rembrandt van Rijn that could be worth £20 million ($30 million Cdn).

The work showing Rembrandt wearing a black cap with two ostrich feathers and a short, decorated velvet cape was previously thought to have been painted by one of the artist's pupils.

But Ernst van de Wetering, a leading expert on the Dutch master, has re-attributed it as a work by the 17th Century painter himself.

'Throughout the decades-long flim-flamming about its provenance, this fine picture has remained resolutely the same, there for us to judge and enjoy on its own artistic merits, regardless of who painted it'— David Taylor, National Trust

It has been at Buckland Abbey in Devon, the former home of Sir Francis Drake, since 2010, when it was donated to the National Trust by the estate of Edna, Lady Samuel of Wych Cross, whose husband Harold, Lord Samuel of Wych Cross, was a great collector of Dutch and Flemish paintings. The painting had previously belonged to the Princes of Liechtenstein.

The work is dated 1635 and signed by Rembrandt, but the artist operated a large studio in which his pupils emulated his style and composition. In 1968, another Rembrandt specialist, Horst Gerson, suggested it may have been painted by one of the artist's pupils.

That decision was based on what was known about the painter’s style in 1968.

Renewed understanding of Rembrandt's style

Van de Wetering, who is the chairman of the Rembrandt Research Project and a leading expert on the painter, said he based his decision that the work was done by the Dutch master himself on an X-ray of the painting published in 2005 and a renewed understanding of Rembrandt’s style.

"Over the past 45 years we have gathered far more knowledge about Rembrandt's self-portraits and the fluctuations in his style," he said.

He said the painting's crude brushwork and painting technique is observed in other paintings from the early stage of Rembrandt's career.

The painting will hang a Buckland Abbey for another eight months, then be sent for cleaning and further examination, including X-rays, examination of paint pigments, infrared testing and tree-ring dating of the beech panel it is painted on.

The portrait is the only Rembrandt in the National Trust's collection of approximately 13,500 paintings and one of the most valuable paintings it owns. The heritage institution, which runs dozens of British monuments and historic buildings, will not be selling it.

David Taylor of the National Trust said he hoped the news the painting is likely by Rembrandt himself would encourage more people to come to see it.

Lots of Rembrandt self-portraits

“Throughout the decades-long flim-flamming about its provenance, this fine picture has remained resolutely the same, there for us to judge and enjoy on its own artistic merits, regardless of who painted it,” he said in a statement.

Rembrandt "produced a huge number of self-portraits throughout his career, partly because he had a ready subject matter in himself, through which he could develop his painting technique but also because, as he was already famous, the finished images were highly desirable pictures for collectors,” Taylor added.

With files from the Associated Press