Langton Dennis was born in Streatham, Surrey [now London], England on 11 January 1865. From 1882 to 1886 he was articled to Sir Ernest George (1839-1922) and Harold Ainsworth Peto (1854-1933). He then attended the Royal Academy Schools in London in 1885. In 1887-88 he was an assistant to Thomas Edward Collcutt (1840-1924), and then assistant to Frederick George Knight (?-1930) from 1888.
In 1889 Dennis was elected an Associate of the Royal Institute of British Architects (ARIBA) and subsequently commenced practice practice in London. By 1914 he had relocated his practice to Crowborough in Sussex, where remained until at least the late 1920s. From the early 1920s (and possibly earlier) until at least the early 1930s, he was in partnership with Richard C. Ball (?-c.1969) as Dennis & Ball.
A drawing of a house at Crowborough, Sussex, designed by Dennis is featured in 'The Studio Yearbook of Decorative art' 1907 (p.13); a photograph and ground- and first-floor plans of 'Forest House', Crowborough, Sussex, designed by Dennis are featured in 'The Studio Yearbook of Decorative Art' 1908 (illustration B46); and a drawing and plan of 'Warren Hill', Crowborough, Sussex, are featured in 'The Studio Yearbook of Decorative Art' 1910 (p.29).
Dennis exhibited at the Royal Academy, London, in 1906. He died in Crowborough on 10 March 1945.
In addition to numerous private houses in the counties of Sussex and Surrey, projects by Dennis included Court House at Peel on the Isle of Man (1892-93); Forest House, Aviemore Road, Crowborough (1903); his own house, Offley, Poundgate, Crowborough (1905); Warren Hill, Crowborough (1906); Windlesham, Crowborough, for Sir Arthur Connon Doyle (c.1908); additions and alterations to Crowborough Cottage Hospital (with Richard C. Ball (1924); St John's Church (with Richard C. Ball), Withyham (1930); additions to Upper Gatton Park in Merstham, Surrey; additions to North Park, Epsom Downs, Surrey; a riding school at Burgh Heath, Surrey; and hunting stables in Melton Mowbray, Leicestershire.
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