Jenna Coleman is to play a young Queen Victoria in ITV's new drama series Victoria, after quitting her role as Doctor Who assistant Clara Oswald.
"I have left the Tardis - it's happened," she told BBC Radio 1 on Friday, following reports earlier this week. "I've filmed my last scenes."
After three years on the show, Coleman revealed her exit would air on BBC One "at some point this season".
She will play Queen Victoria from the age of 18 as she ascends to the throne.
The actress said she was "delighted" to be starring in "ambitious" ITV drama Victoria, which will chart the early years of the monarch's 63-year reign and her courtship and marriage to Prince Albert.
"She is a vivid, strong, inspirational and utterly fascinating woman in British history and I can't wait to tell her story," said Coleman.
The actress, who has also starred in Death Comes to Pemberley, Dancing on the Edge and ITV soap Emmerdale, first joined Doctor Who in 2012 alongside former Doctor Matt Smith.
She told Radio 1 Breakfast show host Nick Grimshaw it had been "emotional" leaving the show and filming her last scenes as Clara Oswald with current Doctor Peter Capaldi.
"It's been in the works for a very long time," she said, "[Writer] Steven [Moffat] and I sat down a year and a half ago and tried to work out the best place to do it and tell a really good story.
"We're not going to give any details but it will happen at some point this season... We worked out a really good story arc out so hopefully people will love it."
Coleman is about to start filming ITV's Victoria in locations around the North of England. It is being made by the producers of Poldark and has been written by acclaimed novelist Daisy Goodwin who makes her screenwriting debut with the series.
"I needed to learn to waltz, play Beethhoven," Coleman said of the role on Radio 1, "It's really fun, it's like bootcamp."
Queen Victoria, who was the UK's longest serving monarch until being overtaken by Elizabeth II earlier this month, has previously been portrayed on screen by Emily Blunt in 2009 film Young Victoria.
Coleman said she was looking forward to getting started but that it had been a tough decision to quit Doctor Who.
"There are not a lot of jobs where you get to have an alien as your best mate and get to run away from monsters... it's been so much fun, I love it," she said.
"It's such a unique beast it's been really special."
The ninth series of Doctor Who, which will be Coleman's last, debuts on BBC One tomorrow night, Saturday 19 September.
"I think I'm in denial," added Coleman. "I see Peter all the time and I still see Matt all the time, so I kind of believe I still have the keys to the Tardis."