After Diana Wynyard passed away, she replaced her and appeared in "The Master Builder" with Michael Redgrave and Maggie Smith as part of the new National Theatre Company in 1964. She and Smith would later appear together in The Prime of Miss Jean Brodie (1969).
Daughter Kate Fleming wrote her mother's biography titled "Celia Johnson" (1991).
Her daughters Kate and Lucy Fleming have bought out the literary estate of their uncle Ian Fleming (creator of James Bond). Kate Fleming's father-in-law was the late Liberal politician Jo Grimond (Lord Grimond, Life Peer) and her mother-in-law Laura, Lady Grimond (nee Bonham Carter) was a descendant of the Liberal Prime Minister H.H. Asquith (the 1st Earl of Oxford & Asquith).
Her father was a physician to the Duke and Duchess of York, who later became King George VI and Queen Elizabeth.
Her feature film debut, In Which We Serve (1942), was also that of both Richard Attenborough and Juliet Mills.
Her husband of 36 years was travel writer Peter Fleming, who was the elder brother of author Ian Fleming of "James Bond" fame. They had three children: son Nicol and daughters Kate and Lucy Fleming, who is also an actress, most notably in the series "Survivors" (1975).
Parents were Robert Johnson and Ethel Griffiths; she was the second daughter.
She was awarded the Dame Commander of the Order of the British Empire (DBE) for her services to drama.