A portrait by Venetian painter Rosalba Carriera has sold at auction for more than 20 times its estimate, fetching over £500,000.
The sum is a world record for a work by Carriera, who died in 1757, according to Cheffins auctioneers in Cambridge.
The painting, a portrait of Coulson Fellowes, who was MP for Huntingdonshire from 1741 to 1761, had a pre-sale estimate of £15,000 to £25,000 but went for £508,000.
It was the first time the work had come to market since it was painted 301 years ago.
The portrait was sold to a UK-based private collector via telephone.
It was painted in 1724 and recorded in Carriera's diary when Fellowes visited her Venetian studio.
Fellowes is shown in the portrait as a young man before he became an MP. He was the son of barrister William Fellowes, of Eggesford, Devon.
The portrait was part of the Fellowes family collection at Shotesham Park near Norwich until the sale of the house and estate following the death of Maj Charles Fellowes in 1979, but it remained in the family.
Carriera, who was one of the most fashionable artists of her day, created portraits of many notable figures, including Louis XV of France, English author Horace Walpole and French painter Antoine Watteau.
Her works are in the Louvre in Paris, The National Gallery in London, The Frick Collection in New York and other major galleries.
The previous sale record for a Carriera painting was £421,250, for a portrait of Irish soldier and politician Gustavus Hamilton sold in New York in 2002, Cheffins said.
The auctioneer's Luke Bodalbhai said the Fellowes painting exhibited Carriera's "talent as one of the leading lights of 18th Century portraiture".