Law has worked extensively in television, including appearances in Dixon of Dock Green, Rumpole of the Bailey and the 1972 adaptation of the Lord Peter Wimsey tale The Unpleasantness at the Bellona Club.
She has appeared in films such as Peter's Friends (1992), Much Ado About Nothing (1993) and The Winter Guest (1997).
In 2007 she guest-starred in two Doctor Who spin-off adventures - as Bea Nelson-Stanley in The Sarah Jane Adventures story Eye of the Gorgon and as Beldonia in the audio drama Doctor Who: The Bride of Peladon. Also in 2007 she played Aunt Auriel in the drama Kingdom starring Stephen Fry.
She was married to Eric Thompson until his death in 1982. Their two children Emma and Sophie Thompson are both actresses. She has appeared in many documentries and interviews concerning her late husband's work on The Magic Roundabout.