De Chair was the younger son of Admiral Sir Dudley Rawson Stratford de Chair, KCB, KCMG, MVO, and Enid, daughter of Henry William Struben, of Transvaal, South Africa. The de Chair family were of Huguenot origin, descending from Rene de la Chaire, whose grandson, Jean Francois, Councillor to Charles IX, was created a Marquis in 1600 by Henry IV. The family became English gentry through generations of clergymen.^[1] He married firstly, on 8 October 1932, Thelma Grace (1911–1974), daughter of Harold Dennison Arbuthnot, of Merristwood Hall, Worplesdon, Surrey. They had two sons: Rodney Somerset and Peter Dudley, and divorced in 1950.^[2]

He married secondly, in 1950, Mrs (June) Carmen Appleton, daughter of A. G. Bowen, of Brabourne, Kent. They had two sons: Rory and Somerset Carlo, and divorced in 1957.^[3] In 1958 de Chair married his third wife, Mrs Margaret Patricia Manlove, daughter of K. E. Field-Hart; they had a daughter, Teresa Loraine Aphrodite (who married Sir Toby Clarke, 6th Baronet).^[4] The third marriage ended in divorce in 1974, and that year he married his fourth wife, Lady Juliet Wentworth-Fitzwilliam, only child of Peter Wentworth-Fitzwilliam, 8th Earl Fitzwilliam, who had divorced Victor Hervey, 6th Marquess of Bristol in 1972. Somerset and Lady Juliet had a daughter, Helena, who married Jacob Rees-Mogg. The hurdler Sir Charles Lawrence Somerset Clarke, 7th Baronet is his grandson and the Member of Parliament Theo Clarke is his granddaughter.

Somerset de Chair was educated at The King's School, Parramatta in New South Wales between 1923 and 1930 before attending Balliol College, Oxford.

He was Conservative MP for South West Norfolk between 1935 and 1945, losing his seat by 53 votes. He was one of the Conservatives who voted against the government in the Norway Debate in May 1940. He then served as a Parliamentary Private Secretary in 1942–44. De Chair returned to Parliament as MP for Paddington South from 1950 to 1951. Many years later, in 1994, he stood in that year's European Parliament elections as the "Independent Anti European Superstate" candidate for Essex North and Suffolk South, coming in fourth place with 12,409 votes.

Since he had been a cadet in the Officers' Training Corps at Oxford, De Chair qualified for a commission as a Reserve Second Lieutenant of the Life Guards in 1938. He was mobilised on 24 August 1939, a few days before the United Kingdom's entry into World War II. He served as an intelligence officer with the 4th Cavalry Brigade during the Anglo-Iraqi War and the Syrian Campaign where he was wounded on 21 June 1941. Later service was with the General Staff with the rank of Acting Captain.^[5]

De Chair wrote historical non-fiction, a number of now largely neglected novels, one play, three collections of poetry, and several works of autobiography. He also edited several volumes of the memoirs of Napoleon in English.^[6]

De Chair was known for his extravagant taste and lived in a series of large country houses. He lived between 1944 and 1949 at Chilham Castle and leased Blickling Hall former home of the Marquess of Lothian from The National Trust.^[7][8] He owned St Osyth's Priory in Essex from 1954 until his death in 1995, and also bought Bourne Park House in Kent with his last wife, Lady Juliet Wentworth-Fitzwilliam.

• Leigh Rayment's Historical List of MPs
• everything2.com

• Hansard 1803–2005: contributions in Parliament by Mr Somerset de Chair