Netflix reveals who will play Princess Diana in The Crown
Grantchester actor Emma Corrin will play Lady Diana Spencer in the royal drama – but the character won't make an appearance until season four
However, Netflix has confirmed that the key royal figure will not make an appearance on screen until season four.
Season three is due to be released on Netflix later in 2019, while season four will begin filming later this year according to Netflix.
Up-and-coming British actor Corrin has featured in ITV period drama Grantchester, and is also set to appear in Batman prequel TV series Pennyworth.
However, her appearance as Diana in The Crown is set to be her highest profile role to date.
"I have been glued to the show and to think I'm now joining this incredibly talented acting family is surreal," Corrin said.
"Princess Diana was an icon and her effect on the world remains profound and inspiring. To explore her through Peter Morgan's writing is the most exceptional opportunity and I will strive to do her justice!" she added.
After the news was announced, Corrin said on Instagram that she was "over joyed, over the moon and incredibly honoured".
The third season of The Crown ushers in an entirely new cast, with Olivia Colman replacing Claire Foy as the Queen and Tobias Menzies stepping into Matt Smith's role as Prince Philip.
Helena Bonham Carter meanwhile replaces Vanessa Kirby as Princess Margaret.
While Diana will not feature until season four, The Crown season three is set to include the first appearance of Prince Charles' second wife Camilla Parker-Bowles.
Call the Midwife star and Killing Eve writer Emerald Fennell is set to play the future Duchess of Cornwall.
Season three is expected to be released at some point in 2019, although Netflix has not yet confirmed an exact date.
While the first two seasons were released in November 2016 and December 2017 respectively, the introduction of a brand new cast has meant a longer wait for the third season.