 Adrian Harris – John Le Mesurier 
 James – Jack Hedley 
 Simpson – Vincent Ball 
 Blake – Neil McCallum 
 Thomas – Jon Laurimore 
 Sir Arthur Harris – Lyndon Brook 
 Lady Emma – Diana Fairfax 
 Michaelov – Richard Marner 
 Duty clerk – Terence Bayler 
 Craig – John Quentin 
 Schoolmaster – John Saunders 
 Young Adrian – Sean Maddox 

Better known for comedic roles, Le Mesurier's casting was a brave move, one which initially concerned the actor who "was very, very scared" that "he wouldn’t be able to pull it off".Le Mesurier would later call the role 'the best part I ever had on TV'.While reviews of the play were mixed, critics were unanimous in their praise for Le Mesurier and he won the British Academy Television Award for Best Actor in 1972.