The First Doctor Who
The very first Doctor Who was played on television by William Hartnell between 1963 and 1966, covering 3 complete series and the first two episodes in series 4.
One of the most sought after episodes of Doctor Who is "The Tenth Planet" where the first Doctor is seen to regenerate for the very first time and become the second Doctor.
Unfortunately between 1964 and 1974 a large amount of material in the BBC libraries were destroyed or wiped and as such no surviving copy is known.
The Doctor at this time progressed in character from a selfish anti-hero into a more noble, helpful and gracious figure during these early series.
As the first Doctor, William Hartnell is generally considered to set the underlying character of the Doctor and elements of his portrayal are evident in the performances of all his successors.
There have also been two movies featuring the first Doctor and the Daleks and the role of the Doctor in these films was played by Peter Cushing.