John Alan Slater was born in Hampstead, Middlesex [now London], England in 1885, the son of the architect John George Slater (1847-1930). After studying at Cambridge University, he was articled to Sir Aston Webb (1849-1930) from 1908 to 1910. He also attended the Architectural Association Schools and the Royal Academy Schools in London. He then worked as an assistant in his father's practice, Slater & Keith, in London. He qualified as an architect in 1910 and in c.1910 became a partner in the practice. The practice was dissolved in 1924 following the death of John George Slater.
John Alan Slater subsequently formed a partnership with Arthur Hamilton Moberly (1886-1952) as Slater & Moberly. In 1932-36 they designed the Peter Jones department store in Sloane Square, London, in collaboration with Charles Herbert Reilly (1874-1948) and William Crabtree (1905-1991). In 1936 Reginald Harold Uren (1906-1988) joined the practice which was renamed Slater, Moberly & Uren
John Alan Slater was elected an Associate of the Royal Institute of British Architects (ARIBA) in 1911 and a Fellow of the Royal Institute of British Architects (FRIBA) in 1925. His address was given as 11, St John's Wood Park, London in 1911; 6, Temple Fortune Court, Golders Green, London in 1911 and 1914; 46, Berners Street, London He died in London on 16 June 1963
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