A painting owned by The National Gallery was once in the possession of Adolf Hitler, an expert has claimed.
Dr Birgit Schwartz, who is researching Hitler's art collection, says Cupid Complaining To Venus once hung in the Nazi leader's private gallery.
She made the discovery while studying photographs from his personal library.
A gallery spokesman said they had "no reason to doubt the claim" and appealed for anyone with information about the Lucas Cranach painting to come forward.
The gallery bought the painting in 1963 from New York dealers E&A Silbermann.
It shows Cupid holding a honeycomb and telling Venus that he has been stung by bees.
The National Gallery said it had only recently learned that the portrait was acquired in 1945 by Mrs Patricia Lochridge Hartwell, an American war correspondent in Nazi Germany.
A relative of Mrs Hartwell said she had been allowed to take the painting from a warehouse full of art which was controlled by US forces in Southern Germany.
Mrs Hartwell eventually brought the painting back home to the US.
Part of the gallery's work is to investigate the provenance of its paintings.
Concerns that some works may have been seized by the Nazis during World War II have led to it paying particular attention to the whereabouts of its paintings between 1933 and 1945.
The gallery now wishes to establish how and when Cupid Complaining to Venus came to be in Hitler's collection.