Leslie Mansfield was born in Frant, near Tunbridge Wells, Kent on 16 November 1885 and was articled to Edward John May (1853-1941) from 1904 to 1907. He also attended classes at the Architectural Association Schools. He subsequently worked as an assistant to Gerald Callcott Horsley (1862-1917), to Charles Francis Annesley Voysey (1857-1941), to William Adam Forsyth (1872-1951) and Hugh P. G. Maule (1873-1940) of Forsyth & Maule; and to Francis Hugh Greenaway (1869-1935) and John Ernest Newberry (1862-1950) of Greenaway & Newberry.
Mansfield qualified as an architect in 1910 and was elected an Associate of the Royal Institute of British Architects (ARIBA) later that year and A Fellow of the Royal Institute of British Architects (FRIBA) in 1921.
He commenced independent practice in London in 1911 and was active as an architect until at least the late 1920s.
Mansfield's name doesn't appear in The R.I.B.A. Kalendar after 1927. He died on 8 January 1965. His address at the time of his death was given was given as 4 Harbour Cottages, Bosham, near Chichester, Sussex
Extensive works at London Aerodrome, 1913 and 1914; aeroplane factories in 1914 and 1915; fish shop at 46, Old Bond Street, W., 1919: private picture galleries, 1923-25; "The Aquarium," Wembley, 1924. Domestic work In London and Provinces. [Source: Who's Who in Architecture 1926]
Directory of British Architects 1834-1914. Compiled by Antonia Brodie, et al. Volume 2: L-Z. London; New York: British Architectural Library, Royal Institute of British Architects/Continuum, 2001
Marriott, Charles. Modern English Architecture. London: Chapman & Hall, 1924