William Henry Dashwood Caple was born in Cardiff, Glamorgan, Wales in 1866 and was articled to Edwin Montgomery Bruce Vaughan (1856-1919) in Cardiff from 1881 to 1885. He also studied at the South Kensington School of Science and Art in London. After working as an assistant in various architectural offices in London, he commenced practice in Cardiff in 1888.
Caple was Diocesan Surveyor for Birmingham and was Deputy Housing Commissioner and Housing Commissioner (under the Ministry of Health). He designed a number of schools including intermediate schools in Llanelli, Wales in the 1890s and the Truant Industrial School in Cardiff in 1897.
He was elected a Fellow of the Royal Institute of British Architects (FRIBA) in 1907. His address was given as Llandff House, Llandaff, Wales in 1906; 2 Church Road, Cardiff, Wales in 1806 and 1926; Queen's College, Birmingham in 1923 and 1926; 50 Wellington Road, Edgbaston, Warwickshire in 1930; and 5 Porchester Square, London in 1939. He died on 23 January 1939. His death was registered in Paddington, London
Directory of British Architects 1834-1914. Compiled by Antonia Brodie, et al. Volume 1: A-K. London; New York: British Architectural Library, Royal Institute of British Architects/Continuum, 2001