George Bernard Shaw wrote his play "Saint Joan" specifically for her, and she performed it in its original production.
1931: Appointed a DBE, and a Companion of Honour in 1970.
1966: Created an honorary DLitt of the University of Oxford.
Both she and husband Sir Lewis Casson took a keen interest in politics and were supporters of the Popular Front government in Spain during the Spanish Civil War, which was fighting against the Nazi-supported forces of Francisco Franco. She joined Emma Goldman, Rebecca West, Fenner Brockway and C.E.M. Joad in establishing the Committee to Aid Homeless Spanish Women and Children. Both she and Lewis held strong politically leftist beliefs and were active members of the Labour Party, to the extent that when the 1926 general strike cut short the run of "Saint Joan", they remained strongly on the side of the strikers. On a trip to South Africa in 1928, she and Lewis aggressively fought segregation so black theatergoers could experience their presentations.
Considered by many critics to be one of the greatest actresses of the 20th century.
First British actress to appear on a postage stamp
Grandmother of Glynis Casson.
In 1940, during WWII, her son John, who was in the military, was reported missing and presumed dead. She and her husband had no further news about him until the war ended in 1945 and they found out he had been captured and was still alive. He was home within a few weeks.
She severely damaged her voice on a tour of the US presenting Shakespeare plays in 1905. Vocal problems would continue to plague her for the rest of her career.
She was portrayed by Sian Thomas in the original production of the play "Fram", by Tony Harrison , which premiered at the National Theatre, London, UK in April 2008.
She was superstitious about washing her stage costumes, and would not allow anyone else to touch them.
Sister of actor Russell Thorndike.
Sybil and husband Sir Lewis Casson were involved in the early days of British Equity, The Arts Council, The Old Vic, the National Theatre, Chichester Festival Theatre and, of course, the Thorndike Theatre in Leatherhead, which has since closed. Both Dame Sybil and Sir Lewis died at the ages of 93. Lewis died in May of 1969, a few months before the opening of The Thorndike Theatre in September.
Was nominated for Broadway's 1957 Tony Award as Best Actress (Dramatic) for "The Potting Shed."