His parents were Sir George Reresby Sitwell, fourth baronet, genealogist and antiquarian, and Lady Ida Emily Augusta (née Denison).

"[1] In 1911 he joined the Sherwood Rangers Yeomanry but, not cut out to be a cavalry officer, transferred to the Grenadier Guards at the Tower of London from where, in his off-duty time, he could frequent theatres and art galleries.

He acted as best man at the wedding of Alexander, 1st Marquess of Carisbrooke, son of Prince Henry of Battenberg and Princess Beatrice of the United Kingdom, on 19 July 1917 at the Chapel Royal, St. James's Palace, London.

[2] In 1918 Sitwell left the Army with the rank of Captain, and contested the 1918 general election as the Liberal Party candidate for Scarborough and Whitby, finishing second.

In Who's Who he ultimately declared of his political views: "Advocates compulsory Freedom everywhere, the suppression of Public Opinion in the interest of Free Speech, and the rationing of brains without which innovation there can be no true democracy.

"[1] Sitwell campaigned for the preservation of Georgian buildings and was responsible for saving Sutton Scarsdale Hall, now owned by English Heritage.

[10] Sitwell's first work of fiction, Triple Fugue, was published in 1924, and visits to Italy and Germany produced Discursions on Travel, Art and Life (1925).

[citation needed] Sitwell went on to write several further novels, including Miracle on Sinai (1934) and Those Were the Days (1937) neither of which received the same glowing reviews as his first.

[18] Sitwell knew that, because of the libel issue, the poem could not be published in his lifetime; he decided that publication should wait even longer than that to avoid "pain to those still living".

[19] The poem was first published posthumously in 1986, the year the Duchess of Windsor (as Wallis had become) died, in a book entitled Rat Week: An Essay on the Abdication.

"[22] Sitwell's autobiography was followed by a collection of essays about various people he had known, Noble Essences: A Book of Characters (1950), and a postscript, Tales my Father Taught Me (1962).

The sometimes acidic diarist James Agate commented on Sitwell after a drinking session on 3 June 1932, in Ego, volume 1, "There is something self-satisfied and having-to-do-with-the-Bourbons about him which is annoying, though there is also something of the crowned-head consciousness which is disarming."

He spent his last years in Italy, at the Castle of Montegufoni [it; fr], in Montespertoli near Florence, which his father had bought derelict and restored as his personal residence; he died there on 4 May 1969.