The two-hour episode will air at 8.30pm on Wednesday 25 December on ITV and introduces American film star Paul Giamatti as Cora’s brother, alongside the return of Shirley MacLaine as Martha Levinson.

The official synopsis reads: “It’s the summer season and as part of Rose’s ‘coming out’ she is to be presented at Buckingham Palace. The family and servants are at Grantham House, their London residence, preparing for the busy social program.

“Not one to miss such a grand occasion, Cora’s mother, Martha Levinson makes the journey from New York with her playboy son Harold, fresh from his recent brush with the law. Both outspoken and larger-than-life, they make quite an impression amongst certain members of London’s high society, in particular with Lord Aysgarth (James Fox).

“Isobel finds herself with an admirer while Edith is wrestling with a moral dilemma. Downstairs, Daisy gets an unexpected invitation and Carson treats the staff to a special day out. When the Crawleys are implicated in a scandal that threatens to engulf the monarchy, Robert will go to great lengths to protect the royal family, and his own.”

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