The announcement was made on The Crown's Instagram. The 64-year-old takes over from Helena Bonham Carter, who played the part in season three and season four and from Vanessa Kirby, who portrayed Margaret in seasons one and two.
"I could not be happier to be playing Princess Margaret," the British actress said in the announcement.
"The baton is being passed on from two formidable actresses and I really don't want to let the side down."
Lesley also gave a special mention to Imelda Staunton, who will take over the role of the Queen.
"Furthermore, to play siblings with my dear friend Imelda Staunton will be nothing short of a complete joy," she added.
Lesley is an award-winning actress who has appeared across television, film and theatre. She is known for her work on the British soap opera Emmerdale (1974–1976), her Academy Award-nominated performance in Phantom Thread (2017) and for her role in British sitcom Mum (2016-2019). She recently appeared in Maleficent (2017) and in the 2019 sequel Maleficent: Mistress of Evil.
Imelda's part was confirmed back in January. The Harry Potter actress takes over the role from Claire Foy, who played Her Majesty in season one and two, and from Olivia Colman, who portrayed the monarch in season three and the forthcoming fourth season.
Details of the season five script haven't been confirmed, but it is likely it would look at events such as the childhoods of Prince William and Prince Harry and the deaths of Princess Diana, Margaret and the Queen Mother.
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