Season 4 ends on the 1st July 1967, and Season 5 begins just 8 weeks later on the 2nd of September. Season 5 is 40 weeks long. Imperceptibly Doctor Who is beginning to be on Television less.
Perhaps this is one of the reasons for the drop in viewing figures? Has the public got bored with too much Doctor Who? After all, since November 1963 there have only been 27 Saturdays without the Doctor. We shouldn't be tempted to blame the drop in viewers solely on the show though, or on the change of Doctor, as at least 2 million less tuned in to the start of Season 4. In comparison, Season 5 is doing far better, and the fact is that the viewing figures for this, Patrick Troughton's 2nd year, are remarkably consistent (if remarkably average). Of course, 5 years after the Doctor's debut in 1963, the Television landscape has changed remarkably. Science Fiction on British TV is now a popular concept (due in no small part to Doctor Who itself), and perhaps Doctor Who is no longer as groundbreaking or unique as it once was.
The season opens with fan-favourites the Cybermen in their 2nd outing after their debut in "The Tenth Planet". Although history firmly places the Cybermen second only to the Daleks in popularity, there's not much evidence of that popularity here. "Tomb of the Cybermen" starts off at the 6 million mark, and climbs to almost 7.5, before dropping back to just over 6 again for the next 6 part story "The Abominable Snowmen". As we can see from the graph, this pattern repeats across the whole of Season 5, as viewers drop slightly at the beginning of an adventure, climb slowly as the story progresses, then drop back again.
Already we are seeing that viewers are no longer following Doctor Who as a serial drama made up of individual weekly shows. Instead the show has become episodic drama, with clear delineations between each story, and the viewers are starting to follow this. Perhaps the fact that there are clear indications of when a story begins and when it ends helps viewers to decide whether or not to watch next week. Doctor Who retains a slight sense of continuity across the season however, with the start of each new story still beginning with a recap of the end of the previous one.
But with the occasional peak above 8 million viewers, and one dip just lower than 6, Season 5 ends as it began, with the Cybermen, and hovering around the 6.5 million mark.