<span class="SFPTagline"> From SCIFIPEDIA </span>

Doctor Who, Season 4 would bring shocking change to fans of the program. Lead actor William Hartnell was becoming increasingly difficult to work with. He suffered from arteriosclerosis, commonly known as hardening of the arteries and it was obviously beginning to affect him both mentally and physically. But this was not the key problem. Perhaps due to his illness or perhaps due to the loss he felt after the departure of his original castmates, the actor increasingly exhibited the irrascibility of his onscreen persona when the cameras were off. Coupled with the fact that the program's ratings had dropped sharply the previous season, producer Innes Lloyd and BBC management became convinced that it was time for change. It was decided that Hartnell would appear in only two stories in season 4.

A new actor, Patrick Troughton, would be cast in the lead role. This, however, posed the obvious questions of "How do we explain this?" and "How will the new actor portray the character?" The first question was quickly answered by script editor Gerry Davis, who simply suggested the since the Doctor was an alien, perhaps members of his race had the ability to periodically renew themselves, changing into much younger versions who may appear somewhat different than the older version. The concept would soon come to be known as "regeneration."

The second question was more difficult. After much discussion, the production team finally decided that the Doctor would now be played as a salty intergalactic sea captain. But, this idea was vetoed by BBC head of drama (and one of the show's original creators), Sydney Newman, who suggested that the Doctor be portrayed as a cosmic hobo. The production team seized on this idea and thought to add additional depth by making the character the somewhat bitter survivor of the destruction of his homeworld (which the program had yet to even give a name to). This had been one of the possibile reasons for the Doctor's exile suggested by the show's creators. David Whitaker, who was charged with writing the new Doctor's introductory story, suggested that the destruction might be due to a war with the Daleks. However, the planetary destruction concept never earned an on screen mention in the classic series. In fact, the Doctor's people and home planet would be revealed to be alive and well a mere two seasons later. Ironically, the entire concept, including the Dalek war, would be used as a key component in the program's revival - nearly 40 years later.

Troughton's portrayal would eventually be lightened to a vaguely clownish hobo: a master of the art of timely retreat, yet mentally 12 steps ahead of his adversaries and easily capable of making fools of them.

By mid-season, it was becoming obvious to the production team that new companion characters Ben and Polly were not working. Feeling that the character Jamie McCrimmon from "The Highlanders" was far more interesting, they chose to keep the character on as a new companion and write Ben and Polly out in the season's penultimate story. Another new companion in the shape of Victoria Waterfield would be added in the season's final tale.

Aside from the Doctor' metamorphosis, the season is notable for the introduction of the Cybermen. Their debut was seen as an attempt to duplicate the incredible success of the Daleks. This became even more important late in the season when Dalek creator Terry Nation began to pitch his infamous creations to American television. Irritated by this development and uncertain that Nation would continue to allow the use of his creations, the BBC decided to write the creatures out in a climactic final battle at the end of the season. They would not appear again as the primary villain for nearly five years.

Additionally, the production team wanted to continue moving away from the less popular historical stories to focus on the show's science fiction elements. "The Highlanders" would be the last purely historical adventure until season 19.

This season began airing on October 9, 1966. The ratings stabilized and even recovered a bit as audiences tuned in to assess the new Doctor. It would be a pattern that would be repeated often in the program's history.

• The Smugglers (4 episodes)
• The Tenth Planet (4 episodes)

(Patrick Troughton assumes the title role)

• The Power of the Daleks (6 episodes)
• The Highlanders (4 episodes)
• The Underwater Menace (4 episodes)
• The Moonbase (4 episodes)
• The Macra Terror(4 episodes)
• The Faceless Ones (6 episodes)
• The Evil of the Daleks (7 episodes)

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