Which actor encouraged Robert Browning to write verse dramas?

The actor who encouraged Robert Browning to write verse dramas was Charles Macready.

Macready, a prominent 19th-century actor and theatre manager, actively worked to persuade leading literary figures of his time to write for the stage. Following this encouragement, Browning dedicated his primary efforts for several years to the creation of verse plays, including Strafford (1837) and a series of works published in the collection Bells and Pomegranates between 1841 and 1846.12