Lancelot Ribeiro was born in Bombay in 1933 to a Catholic family from Goa. He first came to Britain in 1950 to study accountancy and it was during this stay that his creative interests were kindled. He abandoned accountancy and instead from 1951 to 1953 attended life drawing classes at St Martin's, and subsequently travelled through much of Europe before returning to Bombay to work in insurance in 1955.
In 1960 he had a one-man exhibition in the Bombay Art Society Salon, which was a roaring success and was completely sold out. This galvanised his determination to give up accountancy and became a professional painter. As a result of the exhibition's success, he was commissioned to paint a 12-ft mural for Tata Iron and Steel, and acquired as one of his most enthusiastic patrons the nuclear scientist Homi Bhabha, who bought and commissioned several paintings from him. His exhibition at the Bombay Art Society was followed by five others in Bombay, New Delhi and Calcutta. In 1961, Ribeiro was included in the 'Ten Indian Painters' exhibition, followed by an extensive tour through India, Europe, the US and Canada.
In 1962 Ribeiro came to live in London on a permanent basis, and lived with his half brother, the artist Francis Newton Souza, acting as his studio assistant, as well as painting in his own right. He had begun by painting in traditional oils, though even his earliest-surviving works show stylistic independence, incorporating elements of popular Indian graphic art along with touches of New York Abstract Expressionism and hints of Bernard Buffet's skeletal draughtsmanship.
In the Sixties he became increasingly impatient with the time it took for oils to dry and the lack of brilliance in its colour potential. Consequently, he immediately seized upon the new synthetic plastic bases which were coming into use for commercial paints. He worked with major manufacturing companies, such as ICI, Courtaulds and Geigy, who would supply him with sample quantities of their latest paint products.
In 1972 he lectured on Indian Art and Culture for the Commonwealth Institute. In 1976 he was a founder member of a multicultural art group known as the Rainbow Art Group and in 1978 he founded the Indian Artists United Kingdom Group. In London in the 1980s he exhibited mainly in mixed shows, but he had important solo exhibitions at the Gardner Arts Centre, Brighton (1973), Abbot Hall Art Gallery, Kendal (1978) and Leicestershire Museum and Art Gallery, Leicester, a retrospective from 1960 to 1986, which was followed by a big show at the Camden Art Centre in 1987.
In 2013 Ribeiro was the subject of Asia House's annual exhibition. Restless Ribeiro, An Indian Artist in Britain was a major retrospective of his work, where a number of works from his estate were exhibited to widespread critical acclaim.
The artist's daughter commented, "Painting was his life and obsession and if he was ever away from his paints, he would become extremely restless." A private diary scribbling found after his death encapsulated his feelings towards his work: "I twist and turn, curve and straighten without aim or result. Just an escape, an escapist thing into painting impulsively, compulsively, endlessly, tired, tirelessly with or without joy."