Born Pamela Helen Ostrer in either Westgate-on-Sea, Kent or Southend-on-Sea, Essex, Mason was the daughter of Helen (née Spear-Morgan) and Isidore Ostrer, a wealthy Jewish industrialist and banker who became president of the Gaumont British Picture Corporation in the early 1920s. Pamela left school at age 9, and married cinematographer Roy Kellino at age 18 in 1934, thereafter taking the name "Pamela Kellino".
