New Doctor Who star David Tennant said it was "pretty daunting" to play the sci-fi character, as filming of new episodes began in Cardiff.
Ex-Casanova star Tennant, 34, said it was an intimidating role because "the series is so huge".
"I'm aware of all that but I try to keep it in my back pocket and just get on with the job," he added.
A 13-part series of the BBC TV show will follow a Christmas special, with scenes shot in London last week.
Tennant, a long-term Doctor Who fan, also said he was excited about beginning work on the show.
"It's great - you get to play a Time Lord and have a Tardis. You can't knock that," he said.
Revived after a 16-year absence, Doctor Who proved to be a ratings success on its return in March.
Tennant replaced Christopher Eccleston in the lead role, appearing briefly at the end of the last series in June.
Billie Piper returns as the Doctor's companion Rose Tyler
Last week the Doctor's "striking" new outfit was revealed, consisting of a striped suit, trenchcoat and trainers.
Billie Piper returns as companion Rose, with a cameo appearance by Buffy the Vampire Slayer star Anthony Head.
The 60-minute Christmas special tells of the earth being under threat from alien Sycorax and features actress Penelope Wilton.
The Cybermen will return in the new series, and the Doctor and Rose will meet Queen Victoria and an evil race of Cat Women.
One episode will be written by comedian Stephen Fry while The League of Gentleman star Mark Gattis will once again contribute to the writing.