Her sister Katherine Washbourne was a violinist with the British Broadcasting Corporation Symphony Orchestra under Sir Adrian Boult. While performing on stage in the early 1920s, she found that she liked acting and became an actress. In 1948, after numerous stage musical performances, Washbourne began appearing in films.
Her film credits include Billy Liar (1963) and The Collector (1965).
She played Mistress Pearce in 1964"s My Fair Lady, the stern and caustic Mistress Bramson in the remake of Night Must Fall, and the Matron in the 1968 film, If.
She appeared at both the Royal Court Theatre in London and on Broadway in 1970 in David Storey"s Home. In 1975 she appeared on the West End stage with James Stewart in a revival of Mary Chase"s play Harvey, in the role originally taken by Josephine Hull.
In 1981, Washbourne appeared in Granada Television"s television miniseries adaptation of Evelyn Waugh"s novel Brideshead Revisited as Nanny Hawkins.
One of her last television appearances was in Where"s the Key? (1983), a British Broadcasting Corporation play about Alzheimer"s disease. She died, aged 84, in London.