Isabel Diana Colegate (10 September 1931 – 12 March 2023) was a British author and literary agent.
Born in Paddington in London, England, Colegate was the youngest of her parents' four daughters. Her father was Sir Arthur Colegate, while her mother was Winifred Mary, a daughter of Sir William Worsley, 3rd Baronet, and the widow of Captain Francis Percy Campbell Pemberton of the 2nd Life Guards, who had been killed in action in the First World War.
Colegate was a first cousin of Katharine, Duchess of Kent, who was also a granddaughter of Sir William Worsley, 3rd Baronet.
She was educated at Runton Hill School in Norfolk.
In 1952, Colegate, in partnership with Anthony Blond, set up the publishing firm, Anthony Blond (London) Ltd.
Colegate's novel The Shooting Party (1980) was adapted as an award-winning film of the same name, released in 1985 by Castle Hill Productions Inc. In 2010, the novel was adapted for radio by the BBC.
In 1953, Colegate married Michael Fenwick Briggs. The couple had two sons, Barnaby and Joshua, and a daughter, Emily. From 1961 to 2007, they lived at Midford Castle near Bath.
Colegate died on 12 March 2023, at the age of 91.
WH Smith Literary Award for The Shooting Party, 1981
Fellow of the Royal Society of Literature (FRSL), 1981
Honorary MA, University of Bath, 1988
Orlando at the Brazen Threshold, 1971
News from the City of the Sun, 1979
A Glimpse of Sion’s Glory, 1985
The Summer of the Royal Visit, 1991
A Pelican in the Wilderness: Hermits, Solitaries, and Recluses, 2002
Elizabeth Sleeman, International Who's Who of Women, 2002. ISBN 978-1-85743-122-3.
"ISABEL COLEGATE, 1931 –", University of South Carolina.