After rising to fame for his starring role in the 1940s Just William series of British radio and stage productions, Clark began directing theatrical and television productions in both the United Kingdom and the United States.
Before serving in the U.K. Merchant Navy, he performed on a BBC radio show called the Will Hay Programme.
In the early 1980s, he directed a CBS series titled House Calls.
His second marriage -- to the famous actress Lynn Redgrave -- resulted in children named Benjamin, Kelly, and Annabel. He fathered a fourth child, Zachary, with his assistant, Nicolette Hannah.
He and Ray Milland performed together in the 1966 Broadway production of Hostile Witness.