An Antiques Roadshow expert has scored a £750,000 ($1.24 million) art coup — trumping Sotheby’s in the process — by recognizing a lost Thomas Gainsborough masterpiece that he bought for only £67,250 after the auction house failed to identify it.

The landscape, View of Ipswich, first surfaced at an auction in London last December, where it was described as a work by an unknown artist. Philip Mould, who values fine artwork for the BBC1 TV program, spotted the picture in an online auction catalogue and began piecing together clues that convinced him the painting was created by one of Britain’s greatest 18th-century artists. He bid for the landscape over the telephone so he wouldn’t attract suspicion and now, following authentication by several experts, is offering it to the Gainsborough’s House museum in Sudbury for £750,000. Meanwhile, Sotheby’s, which had originally valued the painting at £10,000 to £15,000, could face having to compensate the painting’s vendor for drastically underestimating its worth.

Read more at the London Times.