Media
The unusually hot weather led to the sci-fi series dropping to 6.19 million viewers, or a 41.8% audience share, between 7pm and 7.45pm.
A BBC spokesperson pointed out that the show was still the most-watched programme of the day and continued to be "king of Saturday evening."
Earlier, documentary Doctor Who: The Ultimate Guide had pulled in 2.77 million (23%) while on BBC Three, spinoff Doctor Who Confidential was multichannel's top draw at 677,000 (6.8%).
Casualty was the day's number two with 5.92 million (34.9%), while Murder in Suburbia ranked as ITV1's best-performing show with an average of 3.9 million (22.4%).
Elsewhere, Big Brother dipped to 2.4 million (13.5%), finishing fourth place in the 9pm hour (more).
Ratings data supplied by ViewingFigures.com
More: Media, TV Ratings Roundups
TV Ratings
Big Fat Gypsy Weddings takes nearly 4mThe return of Big Fat Gypsy Weddings draws more than 4.8 million viewers.
Tube Talk
'Simpsons' ultimate countdown (15-11)The countdown of the greatest Simpsons episodes continues.
US TV Ratings
'Cougar Town' returns to ABC with 4.8mAll five major networks were down on Valentine's Day, with ABC suffering the most.
TV Interviews
'Upstairs Downstairs' Neil Jackson Q&ANeil Jackson chats to Digital Spy about Upstairs Downstairs series two.
