Francis Guy Robert Elwes [also known as F. G. R. Elwes, and as Guy Elwes] was born in Belgium on 12 May 1895 and was the son of Gervase Henry Cary-Elwes (1866–1921, a celebrated concert singer. By the late 1890s he had moved to Brigg in Lincolnshire, England. He subsequently moved to London where he established Elwes Ltd., a firm of interior decorators. Photographs of a bedroom suite and chairs designed by Elwes are illustrated in Modern English Furniture by J. C. Rogers (London: Country Life, 1930 pp. 91, 189); and a photograph of a bedroom of a house in London re-decorated by him is illustrated in Design in the Home by Noel Carrington (London: Country Life, 1933 p. 20).
In the 1939 National Register for England Wales, Elwes gave as his occupation Architect and Decorator. He appears not to have been accredited to the Royal Institute of British Architects, and it is not known where or with whom he may have received his training in the profession.
Elwes's address was given as 8 Devonshire Place, London in 1931; The Wood House, Epping, Essex in 1939; and Ham Spray House, Marlborough, Wiltshire in 1966. He died on 25 June 1966. A series pf photographs of Elwes taken by Howard Coster in the 1930s are in the National Portrait Gallery, London.