London (CNN) -- A newly-discovered work by Spanish "Old Master" Diego Velazquez has sold at auction for $4.7 million, after it was spotted in a group of paintings by a largely-forgotten British artist.
"Portrait of a Gentleman" was originally thought to be by 19th century British artist Matthew Shepperson -- but the change of attribution meant it sold for 10,000 times its original estimate.
The work came to light when a descendant of Shepperson put a number of his paintings up for sale in August 2010. As such, it would have been expected to sell for between $320 and $480.
Instead -- following more than a year of tests, X-rays and research -- it was confirmed as a Velazquez, and so became the highlight of Wednesday's old masters sale at Bonhams in London.
Diego Rodriguez de Silva y Velazquez (1599 - 1660) was the leading artist in the court of King Philip IV of Spain, and is best known for his portraits of the royal family, including his masterpiece, Las Meninas.
The identity of the "Gentleman" in the portrait is not known, but it is thought he may be Juan Mateos, the king's master of the hunt.
Andrew Mckenzie, the company's director of old master paintings said the portrait was of "outstanding quality" and had "extraordinary presence."
A spokeswoman for the auction house said that following a lot of interest, the Velazquez work was eventually bought by an American dealer.
She said the company was "very pleased" with the sale, which also saw the world record for a work by Dutch artist Adriaen Coorte smashed when his "Three peaches on a stone ledge with a Painted Lady butterfly" went under the hammer for $3.3 million.