It was the most valuable piece of artwork ever identified in the 36-year history of the Antiques Roadshow.

But the triumph of discovering a rare 17th-century Van Dyck painting was deflated last night after the work failed to sell at auction.

Fiona Bruce, the show's presenter, first spotted the oil painting in December last year and had a hunch it could be a genuine piece by the Flemish artist. After restoration work the painting, called "Head Study of a Man in a Ruff," was verified by a leading authority on Van Dyck.