Tennant announced this year he would be leaving the long-running science-fiction series.
Matt Smith is to take over the role of the iconic time and space traveler. He will be the 11th actor to play the character and the next season of the show is to begin airing in the spring.
Simm, who starred in the British versions of "State of Play" and "Life on Mars," plays The Doctor's nemesis, The Master, in the "Doctor Who" Christmas special. He previously played the recurring role on the show in 2007.
"It's all done," the BBC quoted Simm as saying. "It was a great script and we had such fun doing it. It'll be a brilliant send-off for Mr. Tennant. Last time I did it, it was such fun to do."
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