4.58 million watched Doctor Who, The Magician's Apprentice in the UK, according to unofficial overnight viewing figures.
Doctor Who was the highest rated show on BBC One for the day, just above Casualty, which had 4.34 million watching. The day was won by The X Factor which had an audience of 7.33 million.
Last year's series opener, Deep Breath, Peter Capalidi's first story, had an overnight audience of 6.8 million.
A final figure, including those who record the programme and watch it later, will be released next week, and is likely to show a substantial increase on the initial figure.