Downton Abbey actress Siobhan Finneran, an important supporting actress for the past three seasons, is set to leave the show. The 47 year-old actress, who plays the scheming maid Sarah O'Brien, told the Radio Times that she will not return for season four of the hugely popular period drama.

Mrs O'Brien played an integral role in many of the show's lead plots, including a bitter feud with butler Thomas Barrow, as well as causing Lady Crawley to miscarry. "I'm not doing any more," Finneran revealed, "O'Brien is a thoroughly despicable human being - that was great to play. I actually have great fun being sniffy to everyone. I love O'Brien the most when she's spiteful and has a brilliant put-down. She's a clever lady and a bad enemy to make."

The news will come as the latest surprise to fans of the ITV drama, which has announced the departure of numerous cast members in the past few weeks. Dan Stevens, who played Matthew Crawley, and Jessica Brown Findlay, who played Lady Sybil, have both left the series in the last year while the future of writer Julian Fellowes remains to be seen. 

Dan StevensJessica Brown-Findlay
Finneran Follows Dan Stevens [L] and Jessica Brown-Findlay [R] Out Of Downton Abbey

However, Shirley MacLaine, who appeared in season three of the show as Martha Levinson, will return in season four. Several new actors have also been announced for the new series, including Tom Cullen, Harriet Walter and Julian Ovenden. Soprano Kiri Te Kanawa will also appear on the show as "a guest who sings in the house," according to the New York Times.