A portrait of a young and handsome Charles Dickens that was lost for over 130 years has been discovered in a tray of trinkets at an auction in South Africa.

The discovery is one of the most remarkable finds of recent memory. The art dealer Philip Mould, who was instrumental in its identification, said: “I’ve spent a career specialising in British art and this ranks among the most exciting things we have ever discovered. It is the lost portrait.”

It was found last year in a general sale in Pietermaritzburg in the South African province of Kwazulu-Natal. A man paid the equivalent of £27 for a cardboard tray containing a metal lobster, an old recorder, a brass plate and a small painting which was so covered with mould that the face could barely be made out.

The finder took it out of the frame, which he sold. “He was moments away from basically throwing away this fungus-covered picture and then he started looking at it and realised that the face was very compelling,” said Mould.

With the help of some online research the finder realised it had the look of Dickens, which prompted him to contact Mould’s gallery and the miniatures consultant Emma Rutherford.

“She came to me and said something extraordinary has come up – it has an appearance of the lost portrait of Charles Dickens,” said Mould, who is best known for Fake or Fortune, the BBC One series he presents with Fiona Bruce.

It soon became clear that it must be the lost Dickens portrait by the artist Margaret Gillies, an early supporter of women’s suffrage. It was painted in late 1843 when Dickens, aged 31, was an emerging literary star and writing A Christmas Carol, and it was exhibited to acclaim at the Royal Academy of Arts in 1844.

The poet Elizabeth Barrett Browning was one of those to see it, remarking that it showed Dickens as having “the dust and mud of humanity about him, notwithstanding those eagle eyes”.

It was used as the frontispiece of A New Spirit of the Age, an 1844 book of essays on the cultural stars of the day including Tennyson, Browning and Mary Shelley. Dickens was the first chapter.

There are two other early portraits of Dickens, one of which is at the National Portrait Gallery, but the lost portrait is very different, according to Mould. “Instead of it being a ruminative, authorial-style characterisation with the eyes looking away … here he fixes you with these penetrating but also doleful eyes. They are looking at you. It’s an extremely direct, almost predatory look.”

Rutherford said Dickens was going through a difficult period because of the poor reception of his most recent work, Martin Chuzzlewit.

“To have a portrait of Dickens at this specific time, when his career was on a knife-edge, makes it all the more compelling. His future was uncertain – he was overdrawn with a growing family and living beyond his means. Gillies seems to capture both vulnerability and confidence.”

How the portrait got to South Africa may never be fully known but new research suggests it was given to one of two brothers-in-law of Gillies’ adopted daughter. Both emigrated to South Africa in the 1860s.

The hope is for the portrait to become part of the permanent collection of the Charles Dickens Museum in London. The cost of the portrait is not being disclosed apart from that it is a six-figure sum. The museum is beginning a campaign to raise the necessary funds to acquire the portrait. In the meantime it is going on display at Mould’s gallery on Pall Mall.