Things aren't going too well over at Doctor Who. Halfway through the season, the UK overnight ratings for the show are averaging just 5.23 million viewers. If you discount the season premiere, they are a very low 4.97 million viewers. Sure, Doctor Who is either winning or coming in second in its timeslot. But overall, the show is sinking.
In comparison, Matt Smith's first season as the Doctor had a season average of 5.89 million viewers, and a regular episode season average of 5.72 million viewers. His second season had a season average of 5.75 million viewers, and a regular episode season average of 5.68 million viewers. His third season had a season average of 5.73 million viewers, and a regular episode season average of 5.68 million viewers.
Capaldi's outing as the Doctor started out well, with the highest-rated season premiere since Smith's debut in 2010, and the highest-rated non-Christmas/non-anniversary episode since 2010's "Flesh and Stone" (6.87). But the show quickly shed nearly 400,000 viewers for its first two episodes, and has dropped another 400,000 viewers since.
Deep Breath 6.79(Note: Timeshifted viewing doesn't change the overall trend.)
Into the Dalek 5.20
Robot of Sherwood 5.20
Time Heist 4.93
The Caretaker 4.89
Kill the Moon 4.81