Derry Girls actress Nicola Coughlan will star alongside Dame Julie Andrews in a Netflix adaptation of Julia Quinn's novels about the Bridgerton family.
The news came as the Galway-born actress took a pop at Tory leadership favourite Boris Johnson on Twitter for failing to take part in a vote on same-sex marriage for Northern Ireland.
Johnson posted a photo of himself with revellers at Pride in London last week, tweeting that he would "continue to champion the cause if I am lucky enough to become our country's Prime Minister".
Coughlan retorted: "You abstained from yesterday's equal marriage vote."
She will play sharp-witted Penelope Featherington in Bridgerton, set in the high society of Regency London.
Dame Julie will voice Lady Whistledown, a mysterious gossip writer who will narrate the series, while Younger actress Phoebe Dynevor will star as Daphne Bridgerton and Jonathan Bailey will play Anthony Bridgerton.
Vanity Fair actress Claudia Jessie will play Eloise Bridgerton and Silent Witness star Golda Rosheuvel appears as Queen Charlotte.
The show will centre on eight siblings as they navigate the marriage market in search of romance and adventure.