Gallery owner Archie Parker thought something was amiss when he came across this painting in an online sale catalogue, and he flew to New York to play out his hunch. It paid off.

A painting that lay forgotten in a dusty storeroom for years turned out to be an original by George Stubbs.

The 18th-century English artist is arguably the most famous painter of horses the world has ever known – as such, the painting that was thought to be worth roughly £3-4,000 is now up for sale and expected to fetch around £750,000.

The work is an oil painting measuring 29.5×21 inches, and entitled Two Hacks, the property of Henry Ulrick Reay Esq of Burn Hall Co. Durham and their blue-liveried groom in a landscape. For a number of years it belonged to the Huntingdon Library in California; believing it to be a copy after Subbs they deaccessioned it, putting it up for sale in New York. So little was thought of it that it was actually entered as a lot in a furniture sale, rather than a specialist fine art sale.

Yet it caught the eye of several collectors who had noticed it in the online catalogue. One of them, Archie Parker of the Parker Gallery in London, jumped on a plane to see it for himself – and ended up buying it in the auction.

Two Hacks by George Stubbs

Parker explained to Country Life that he spends hours trawling through auction listings across the world looking for such neglected gems, a task which he admits usually proves thankless. In this instance, his hunch was proven correct: the signed and dated painting (which was produced in 1789) turned out to be genuine after all, and the dealer is set for a major windfall. That windfall isn’t quite as big as he initially hoped, however: the original sale estimate in New York was $3-5,000, but a couple of other dealers had the same feeling, bidding the work up to £175,000.

Still, even after commission, transport and the costs of cleaning this long-neglected piece, there will be a healthy pay-off for Parker – though not quite what he dreamt of. Parker admits to having quietly slipped off to New York, hoping that nobody else had spotted what he did in the Christie’s ‘Living with Art’ sale catalogue.

The painting will be on display at the BADA 2017 fair in Chelsea until Tuesday 21 March, and Parker is excited to put it on display.

“I’m very excited to show this re-discovered work at BADA 2017,” he said.

For a long time it has been hidden in a dark store thought to be a copy. This discovery shows that even the major auction houses can make mistakes.”

Other highlights of BADA 2017 include an abstract drawing by Andy Warhol; a rare chronometer carriage clock; and antique jeweller Sandra Cronan’s bugs and butterflies display. Further information and details of ticketing is available at www.badafair.com