Experts did not believe Gideon Mantell when he told them he had discovered a 200 million-year-old tooth from a giant lizard.

Even the renowned Georges Cuvier, who founded the science of palaeontology, dismissed the find as a rhinoceros tooth.

In fact it was from a dinosaur, only the second to be discovered.

Mantell refused to give up and finally managed to persuade the establishment. The tooth resembled that of a modern iguana, albeit a huge one, so the dinosaur was named Iguanodon.

Cuckfield Museum is marking the 150th anniversary of Mantell's death this week.

The Sussex doctor's wife, Mary Ann, is thought to have discovered the fossil while they were out walking.

Frances Stenlake, curator of Cuckfield Museum, said: "People in the area are unaware of the importance of him and Mary Anne in shaping modern science.

"Mary Ann discovered the fossil at White Man's Green in a pile of stones that had been dumped from a quarry. A monument was built there in 2000 to commemorate the find. I don't think that people give enough credit to her."

Fame did not guarantee happiness however.

Mary Ann rarely left Gideon's side after they married in 1816 and was with him whether at patients' bedsides or in London's lecture theatres.

After his work was finally recognised, Gideon moved to Brighton to concentrate on his fossils rather than his patients.

Mary Ann soon tired of his obsession. The couple and their four children struggled to survive as his work failed to generate the income he expected, and patients deserted him.

Mary Ann left him in 1839 and moved to Lewes with her children, where she remained until his death 13 years later.

Faced with a dwindling bank account, the council came to the rescue and offered to turn his big house into a museum, allowing him one room to live in.

Mantell died alone, having been plagued by years of constant pain following a carriage accident which left him virtually crippled.

Mrs Stenlake is keeping the memory alive, however, and the Cuckfield Museum houses copies of the famous tooth, along with artefacts such as a copy of Mantell's first book on fossils of the South Downs.