Series 4.5 & 5
In 2009 we were treated to a series of special episodes in the lead up to David Tennant's departure. The Next Doctor hit the highest with 13.1 million, the title of the episode implying that it would feature an appearance of the Eleventh Doctor, which it ultimately did not. With Series 5 came Matt Smith as the Eleventh Doctor, whose first episode started off with over 10 million viewers. After that, figures dropped slightly, to between 6 and 8.5 million per episode. S4.5 Average Ratings: 11.49 S5 Average Ratings: 7.7
The Series 4 Specials (Series 4.5) had an Appreciation Index over the mid 80s, which Series 5 generally kept, never dropping lower than 84, and the finale hitting an 89 rating. S4.5 Average AI: 87.6 S5 Average AI: 86.1