The episode had 6.54 million viewers after a week of recordings - a rise of just under two million (1.96 million) on the overnight rating of 4.58 million. Doctor Who was the 13th most watched programme of the week, and the fourth most watched on BBC One.
The episode also had 1.53 million BBC iPlayer downloads in the first week, and the audience for the feature length omnibus repeat of the opening two-parter was 640,000. While these figures will count some repeat viewers and therefore can't be added to the final viewing figure to count the total reach, it's evidence that Doctor Who adds a considerable amount of viewers outside the traditional, recorded means of watching TV.
[Source: Digital Spy]