You have 2 more free articles remaining

The ‘fancy’ portrait was given to the sitter’s father, Robert Lovell Gwatkin, and remained in the family until it was bought by Ferdinand de Rothschild in the 1880s and later bequeathed to Waddesdon Manor.

A second version of the portrait was understood to have been created for the sitter’s family by Reynolds – a picture that later sold at Christie’s in 1905 as a genuine work by Reynolds, fetching 2000 guineas.

Over 70 years later, in 1979, the same work seemingly turned up at Christie’s again, where it sold as a copy of Reynolds and took just £300.

However, an article in The Times, appearing under the headline ‘Reynolds for the price of a frame?’ claimed, on behalf of the buyer, Nicholas Byrne, that Christie’s specialists had failed to notice the 1905 stencil number on the painting’s back and therefore its previous saleroom history.

Nevertheless, it appears expert opinion at the time sided with the Christie’s specialists as no attempt to sell it as a Reynolds was made.

However, it was suggested that it might be one of nine contemporary copies known to have been made from the Waddesdon version by separate artists in 1823.

Subsequently, the portrait entered the collection of a private family, who kept a newspaper clipping of The Times article in the frame but again, it would appear, they never sought to sell it.

In late 2016 it came to Amersham Auction Rooms (15% buyer’s premium) in Buckinghamshire as part of a probate consignment from the family and was offered for sale on February 2 this year.

The picture included the press clipping and had a mid-1950s label to the reverse for Bournemouth dealer Butt & Son. Its Christie’s 1905 number was missing, thought to have disappeared during restoration. With knowledge of the historical debate surrounding the picture, the auction house catalogued the 2ft 6in x 2ft (76 x 61cm) portrait as late 19th century British School ‘in the manner’ of Reynolds, and priced it at £50-100.

“Before the sale I did say that it would either go for £1000 or £50,000. It was a difficult picture to estimate and ultimately I let them make up their own minds,” said auctioneer Dick Ellis.

On the day, several parties pursued it to £1000 before a pair of online bidders took it to £2500. The buyer is thought to be a London dealer.