William Hartnell
(January 8, 1908 – April 23, 1975) was the first actor to portray the Doctor. His run began in 1963 with An Unearthly Child and ended with The Tenth Planet. Hartnell's Doctor was at times Stubborn and cruel, but at other times playful and almost childlike in his enjoyment of adventure.
Hartnell usually played comic characters, until 1944 when he was cast in the robust role of Sergeant Ned Fletcher in The Way Ahead. From then on his career was defined by playing mainly policemen, soldiers, and thugs , though he was noted for his ability to bring complexity to such roles, particularly his widely praised performance as Dallow in Brighton Rock (1947). In 1958 he played the sergeant in the first Carry On film, Carry On Sergeant and in 1963 he appeared as a town councillor in the Boulting Brothers' film Heavens Above! with Peter Sellers. William Hartnell also appeared as Will Buckley in the film The Mouse That Roared in 1959 (again with Sellers).
His first regular role on television was as Sergeant-Major Percy Bullimore in The Army Game from 1957–1961. In 1963 he appeared in a supporting role in the film version of This Sporting Life, giving a sensitive performance as an aging rugby league talent scout known as 'Dad'.
Hartnell's performance in This Sporting Life was noted by Verity Lambert, the producer who was setting up a new science-fiction television series for the BBC, Doctor Who. Lambert offered Hartnell the title role. Although he was initially uncertain, Lambert and director Waris Hussein convinced him to take the part and it became the character for which he gained the highest profile and is now most remembered. Hartnell later revealed he took the role as it led him away from the gruff, military roles in which he was becoming increasingly typecast, and came to particularly relish the attention and affection that playing the character had brought him from children.
Hartnell's poor health (arteriosclerosis) as well as poor relations with the new production team on the series following the departure of Lambert, ultimately led him to leave Doctor Who in 1966. When Hartnell left Doctor Who in 1966, producers of the show came up with a unique idea. Since the Doctor is a Time Lord, he can transform into another man when he dies. Hartnell himself suggested that Patrick Troughton replace him as the Doctor. In Episode 4 of The Tenth Planet, the First Doctor dies and transforms into Troughton's Second Doctor.
Richard Hurndall
Played the doctor only once, taking the place of William Hartnell as the first Doctor in the 25th anniversary episode The Five Doctors.