Lacey made her stage debut, performing with Mrs Patrick Campbell, in The Thirteenth Chair at the West Pier Brighton on 13 April 1925.

[1] Having acted at Stratford and the Old Vic in 1935/36, she returned to both companies in later years: to the Old Vic in 1951 (Clytemnestra in Electra)[2] and 1962 (Aase in Peer Gynt, Emilia in Othello),[3] and to the Royal Shakespeare Company in 1967, playing Volumnia in Coriolanus and the Countess of Rousillon in All's Well That Ends Well.

[1] She made her film debut in 1938 as the secretive nun who wears high heels in Alfred Hitchcock's The Lady Vanishes, in which she was credited as Catherine Lacy.

In 1966/67 she played a malevolent fortune-teller in The Mummy's Shroud and Boris Karloff's insane wife in Michael Reeves' The Sorcerers.

For the latter, she won a 'Silver Asteroid' award as Best Actress at the Trieste Science Fiction Film Festival in 1968.