An established television and comedic actress, Siobhan Finneran made her acting debut in 1986 in the feature film Rita, Sue and Bob Too! She has appeared in a number of long-running British television series, including Coronation Street and Benidorm among others. She has also appeared in the MASTERPIECE production The Amazing Mrs. Pritchard.

Three seasons into playing O'Brien, the scheming lady's maid whom people love to hate, Finneran describes her character as somewhat misunderstood. "I love her. She is funny and witty. I think a lot of the time what gets misconstrued as being rude or unhelpful in a lot of ways is her making sure jobs are done properly. Yes she is cruel and all…but also a lot of things she does are for the good of the house, and for the good of the whole of the staff. I love her because she is not backwards at coming forwards about saying something. I admire that quality in a lot of people in real life."

Finneran, who rarely gets recognized out of costume as her character ("I look different – just a bit. For a start, I don't have those sideburns!"), lives with her husband, British actor Mark Jordan, and their two children on the Lancashire moors.