* The original 1935 film adaptation of "The Thirty-Nine Steps"? This starred Robert Donat as Richard Hannay.
* A specific adaptation of "The Thirty-Nine Steps" from a later date? There have been many adaptations, including a 1959 version with Kenneth More, a 1978 version with Robert Powell, and a 2008 version with Rupert Penry-Jones.
* A stage production of "The Thirty-Nine Steps"? There are many actors who have starred in stage productions, and the cast changes frequently.
Please clarify which version of "The Thirty-Nine Steps" you are referring to!