The BBC reported the depiction of Suffolk rural life, part of series of six large canvases, is one of the most expensive British paintings ever sold.
"The Lock" had been housed in Madrid's Bornemisza Museum, but its owner, Carmen Thyssen-Bornemisza, announced in May she was selling it because she needed money, the British broadcaster said.
"It's very painful for me, but there was no other way out. I need the money, I really need it. I have no liquidity. Keeping the collection here is costly to me and I get nothing in return," she told the Spanish newspaper El Pais.
Thyssen-Bornemisza is a baroness and former Miss Spain title holder whose husband, Swiss industrialist Baron Hans Heinrich Thyssen-Bornemisza, died in 2002, leaving behind a huge private art collection, most of which was sold in Spain.
The BBC did not identify the new owner of "The Lock."
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