Tate to exhibit 'lost' van Dyck

A portrait by the masterly 17th-century Flemish artist Anthony van Dyck, which has never been exhibited in public and whose exact whereabouts were unknown for close to a century, is to be shown at Tate Britain next year.

Katherine, Lady Stanhope, later Countess of Chesterfield, is one of Van Dyck's most powerful portraits and appeared at auction in New York in 2006. It had been kept in a private collection in New York since 1920 and many art historians thought the work had been lost to the public forever.

Van Dyck was the court painter of Charles I and is widely regarded as the outstanding painter of the 17th century.

The portraits of Van Dyck, described as "my best pupil" by his mentor and fellow Flemish Baroque painter Peter Paul Rubens, chronicled the tumultuous years between Charles's reign and the onset of England's civil war.

Van Dyck, the son of a silk merchant, was born in Antwerp in 1599 and came to London in 1620. He is credited with reinventing portraiture in Britain and giving the most lasting artistic rendering of Charles I as monarch.

Tate Britain's major spring exhibition, Van Dyck and Britain, will open on 18 February 2009. Several other rare works, many from the Royal Collection and National Trust, will be on display.