Earlier this year, Colman released a statement via the Twitter page to express her excitement.
'I'm so thrilled to be part of The Crown,' she said. 'I was utterly gripped watching it. A proper 'just one more' feeling. I think Claire Foy is an absolute genius. She's an incredible hard act to follow. I'm basically going to rewatch every episode and copy her.'
Several other cast members have also been replaced.
Tobias Menzies will take over from Matt Smith as Prince Philip and Helana Bonham Carter will take over from actress Vanessa Kirby in the role of Princess Margaret.
Season 3 will premiere in 2019 and will pick up where Season 2 finished, covering the period of 1964 to the early 1970s.
Hear our interview with Rob Mills, plus reviews of Sharp Objects, House Rules, You Can’t Ask That, Get Shorty and Snowfall on WHO’s TV podcast, Binge List. Subscribe on iTunes http://po.st/syE3JF, OMNY http://po.st/VmG0GO, or listen below: