Downton Abbey has lost another star.

With Dan Stevens (Matthew) and Jessica Brown Findlay (Lady Sybil) having already departed the ITV hit, The Huffington Post UK confirms that Siobhan Finneran is also exiting the series.

"I'm not doing any more," the actress said. "O'Brien is a thoroughly despicable human being - that was great to play."

Downton Abbey Season 4 is currently filming in England and will air some time in late 2013 in the United States.

No word yet on the situation from anyone connected with the series and, therefore, no details on just how O'Brien will be written out.

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.