Painter, architect, restorer and teacher William Rondas, known as Willi, was born to an English mother and Belgian father in Brussels, Belgium in 1907 but spent his formative years in England. He initially studied singing and then trained as an architect in Paris, afterwards practising in the Belgian Congo. In 1931 he returned to Paris and studied painting at L’Ecole des Beaux-Arts in Paris and (probably) at the Slade School of Fine Art, London. In Paris he worked with Raoul Dufy, also studying restoration of the Old Masters at the Louvre and assisting the stage designer Christian Bérard. Rondas held his first exhibition at Galerie Le Centaure, Brussels in 1938. During the Second World War he served in the Belgian army before being evacuated at Dunkirk and serving for the rest of the war in the British Army. 

Postwar Rondas was naturalised in Britain and taught in art schools in Croydon and Nottingham, as well as designing for the textile firm Jacqmar and painting a mural in Johannesburg Post Office Tower restaurant. He worked in both a realist and Surrealist style, exhibiting in both Europe and the USA including at the Brooke Street Gallery, London (1944), the Leicester Galleries, London (1948) and Edwin Hewitt Gallery, New York (1952). In the mid–1950s he lived and worked in Belfast, Northern Ireland, holding a solo exhibition at the Gallery, 55a Donegall Place in 1955, with 40 works in oil, gouache, watercolour and pastel, including landscapes of London and Ulster, and works on theatrical and ballet themes. In 1961 he held two solo London exhibitions, showing Surrealist compositions at John Whibley Gallery and landscapes, compositions and nudes, in a variety of styles, at Ben Uri Gallery; he was also a regular exhibitor at the O'Hana Gallery. In 1966 he decorated an Empire style bedroom for an exhibition entitled Romantic Bedrooms of France at Meubles Français in London.

Willi Rondas died in Brussels, Belgium in 1975. In 2018 his work featured posthumously in Exodus: Masterworks from the Ben Uri Collection (Bushey Museum) and Refuge and Renewal: Migration and British Art (Royal West of England Academy, Bristol) in 2019. His work is held in the Ben Uri Collection in the UK and in the Waterloo Museum, Belgium.