An engineer's daughter, she had first planned on becoming a ballerina, using her original Christian name Muguette, but abandoned those plans by the age of 17 when she realized that her physique was more in keeping with her other first name, Megs. She trained in Liverpool at the School of Dancing and Dramatic Art and then joined the Liverpool Repertory Company in 1933 before moving to London to appear at the Player's Theatre four years later.