The First DoctorThe first actor to play the Doctor, William Hartnell portrayed the eponymous alien adventurer for approximately three and a half years between 1963 and 1966, piloting the TARDIS - his blue police call box which was bigger on the inside - across space and time every Saturday at teatime, accompanied by a rotating cast of human friends and companions.
(1963 - 1966)
(1963 - 1966)
In the process, Hartnell became one of the most identifiable and beloved stars of the British small screen in the 1960s, respected by his co-stars, his fans and television critics alike. Many actors have taken the controls of the TARDIS, but none have failed to acknowledge that Hartnell was the originator to whom they are uniformly indebted. He was the gruff but kind, irascible but brilliant grandfather every child wanted, and without him it is impossible to imagine getting off the ground, much less all the way to Galaxy 4.
Nevertheless, all good things must come to an end. With a history of serious health problems dating back to before the Second World War, including undiagnosed arteriosclerosis which had affected his physical capacities and his ability to remember lines, Bill Hartnell had never been an entirely well man. By late 1966 it had become abundantly and tragically clear to all concerned, including the actor himself, that Hartnell would not be able to continue. Hartnell was offered the opportunity to depart the role at the end of the serial "The Tenth Planet", in which the Doctor first encountered the sinister Cybermen, but, mindful that the production staff had not reached a definitive solution to his inability to remain in the real, Hartnell mustered his characteristic determination and soldiered on to complete filming of the next serial, the six episode "The Power of the Daleks", designed to write the villainous aliens out of the series alongside him. 
To the horror and dismay of children across the country, the First Doctor exhaustedly announced that his defeat of the Daleks represented "their final end" before tumbling to the floor in front of his companions, Ben and Polly.
And then, to the surprise of viewers at home as much as the character's friends, the Doctor began to change…
 Hartnell's decision to push himself to complete "Power" despite the objections of his family, friends, co-stars and the series production staff, while widely praised for its determination and commitment, would be equally attributed with precipitating the fast decline in his health which ultimately led to his death in the summer of 1972. Indeed, in the final episodes of the serial, Hartnell was visibly haggard and fragile, spending much of the final two episodes largely immobile.