Bigger on the Inside: A Royal Visit to the Set of 'Doctor Who' One of Britain's most enduring characters and his faithful companion got to meet their second most-famous equivalents - you can decide who is who - when Prince Charles and his wife, Camilla, the Duchess of Cornwall, visited the actors Matt Smith and Jenna Coleman on the set of the BBC science-fiction adventure series "Doctor Who" on Wednesday. BBC America, which broadcasts "Doctor Who" in the United States, said in a news release that Prince Charles and Camilla traveled to the Roath Lock studios in Cardiff Bay, where the show is filmed, to celebrate the 50th anniversary of the series. Their Royal Highnesses were shown costumes and graphic displays and given instructions on how to fly the Tardis, the time-and-space-navigation vehicle used by the Doctor on his adventures, and Prince Charles used a voice-modulating device to simulate the sound of a nefarious alien Dalek. It was not immediately clear how Prince Charles's repeated intonations of the Dalek catch phrase "Exterminate!" were interpreted by his subjects. Mr. Smith, who plays the 11th incarnation of the Doctor, said in a statement that Prince Charles "said he remembers watching the show when he was 15 and seemed very knowledgeable on the "Who" history, so it's nice to think" he and Camilla are watching. Ms. Coleman, who plays his companion Clara Oswald, added that Prince Charles "was particularly interested in the mechanics of how the Tardis works and the storyline for the upcoming 50th anniversary special, but I didn't give too many secrets away." Steven Moffat, the producer and lead writer of "Doctor Who," said that Prince Charles's "attempt at being a Dalek was great," adding: "There would be a part in the show for him if he wanted it." Given that Mr. Smith has recently announced his plans to leave "Doctor Who" at the end of the year, that part could be available sooner rather than later.