The picture was painted by German artist Franz Xaver Winterhalter (1805-73), who completed many portraits of royalty. It shows a woman, thought to be Therese Freifrau von Bethmann, who wears diamonds, a white dress and a coronet of flowers.
The vendor’s family had received the picture as a gift in 1960. During the two-day sale of fine art at the auction house starting on April 11, the lot drew competitive phone bidding before eventually surpassed expectations and taking £155,000.
The oil on canvas painting measures 4ft 3in (1.3m) tall and was offered with a fine contemporary wood, plaster and gilded frame.
The auction also resulted in a record for the artist James Dickson Innes when his oil on board painting The Fairy Mountain took a hammer total of £41,000.