Sotheby's London is to auction a portrait of a monk, credited to Anthony van Dyck, that was previously thought to have been painted by Rubens.

The work, owned by the same French family for at least 200 years, was known as Confesseur de Rubens.

Sotheby's says experts noticed brushwork more characteristic of Rubens' pupil Van Dyck.

Meanwhile, a dealer who rediscovered Van Dyck's A Portrait of a Young Girl, in 2010, has spoken of his find.

Thick paint

The artist's Portrait of a Carmelite Monk, which is estimated to sell for £600,000-£800,000 when it is auctioned on 6 July, was among artworks valued for a family by the Sotheby's Paris office.

The auction house's George Gordon said that the way the monk's head was turned to one side created an impression of spontaneity as opposed to the more formal composition of Rubens' portraits....