Born Shirley Vivian Teresa Brittain CAITLIN in 1930 to Sir George Edward Gordon CAITLIN (1896 - 1979) and Vera Mary BRITTAIN (1893 - 1970). Baroness William's father was knighted in 1970, after her mother died.
She was MP from 1964 to 1979, and 1981 to 1983. She was Secretary of State for Prices & Consumer Protection (1974 - 76) and Education & Science (1976 - 79). She was made a Privy Counsellor in 1974, created a Life Peer in 1993 as Baroness Williams of Crosby, of Stevenage in the County of Hertfordshire, and appointed a Companion of Honour in 2017. She had for the last few days been the 3rd most senior Privy Counsellor (by time in position) after Lord Morris of Aberavon and the Earl of Crawford & Balcarres.