Born in Croydon in 1929 as Sonia Mary Biddlecombe, Graham won a scholarship at the age of sixteen to the Guildhall School of Music and Drama, London. She played in rep theatre in Preston, Farnham, Leatherhead and Wolverhampton; with the Old Vic in London and on a tour of South Africa. Her other London appearances include the Duenna, and the principal girl in the Players Theatre pantomime Beauty and the Beast. Her performance in Meet Me By Moonlight at the Aldwych Theatre led to numerous TV and revue engagements.