After making her stage debut with her father's touring company in 1929 she progressed via provincial repertory to the West End, where she appeared continually from the 1930s to the 1970s.
She married the actor Ralph Richardson in 1944, and the couple regularly appeared together in London, and on tour in the UK, continental Europe, Australia and North and South America.
After a short spell with the Dundee Repertory company in 1931, she made her first London appearance in the same year, as Simone D'Ostignac in Porcupine Point by Gabriel Toyne.
[3] In 1955, together with Sybil Thorndike and Lewis Casson, the Richardsons undertook a long tour of Australia, in Terence Rattigan's Separate Tables and The Sleeping Prince.
[5] During Richardson's long West End run in Robert Bolt's Flowering Cherry (1958), he had three leading ladies in succession: Celia Johnson, Wendy Hiller and finally Forbes.
[4] The title role was played by her old friend Vivien Leigh, whose marriage to Laurence Olivier was on the verge of breakdown; Forbes devoted much time to supporting and comforting her.
[5] In 1962, Forbes played Lady Sneerwell to Richardson's Sir Peter Teazle in John Gielgud's production of The School For Scandal in London, New York and on a North American tour.
Husband and wife were together again in 1964 as Bottom and Titania in A Midsummer Night's Dream, in a tour sponsored by the British Council, playing in South America, Lisbon, Paris, Madrid and Athens.