Complex sentence: He popularised the role of Clown in the harlequinade which formed part of British pantomimes during the 1800s and became a key pantomime performer at the Drury Lane, Sadler's Wells and Covent Garden theatres.
Split into simpler sentences: He popularised the role of Clown in the harlequinade that formed part of British pantomimes during the 1800s. He became a key pantomime performer at the Drury Lane, Sadler's Wells and Covent Garden theatres.