Lionel Gordon Baliol Brett, 4th Viscount Esher CBE (18 July 1913 – 9 July 2004) was a British peer, architect and town-planner. He succeeded to his title on the death of his father in 1963.
Brett was born in Windsor, Berkshire, the son of Oliver Sylvain Baliol Brett, 3rd Viscount Esher, and educated at Eton and New College, Oxford, where he read history. He married Helena Christian Pike (a painter) in 1935 and proceeded to the Architectural Association but left to learn from the traditionalist A. S. G. Butler and then, as a non-qualified partner of William and Aileen Tatton-Brown, he passed the RIBA external exams in the summer of 1939, winning the Ashpitel Prize.
He spent the Second World War mostly in Britain, training gunners in the Royal Artillery, until he went through France and Belgium to witness the surrender of Lübeck and Hamburg. In 1945, he stood as Liberal Candidate for Henley, coming third at the polls.
He formed a partnership with Kenneth Boyd to design new houses as Architect-Planner of Hatfield New Town and wrote the initial report of the Hatfield Development Corporation. In November 1957, some 50 of Hatfield's two-storey terraced houses lost their mono-pitched roofs in a storm and the adverse publicity and financial liability ended his business. From this period, despite not wanting to be known as a country-house architect, he was most proud of small houses in Oxfordshire for Hans Juda and Warwickshire for Lord Dormer. A design for the High Commissioner's residence in Lagos in 1958 was compromised by the taste of an incoming Commissioner's wife. A second practice terminated in 1971.
Esher's real interest was in planning and he carried out a study of York for the government, after which he published York: a study in conservation (1968). After a period as Rector of the Royal College of Art he turned again to writing. A Broken Wave: the rebuilding of England 1940-1980 (1981) was an attempt to chronicle and analyse the achievements of post-war architecture and planning, following on from Parameters and Images: architecture in a crowded world (1970). He served as president of the Royal Institute of British Architects from 1966 to 1967 and was appointed a Commander of the Order of the British Empire (CBE) in 1970.