She is the second-eldest of three sisters. Siobhan started acting in a wacky British TV comedy sketch called Alfresco (1983) (1982/1983), co-starring with Robbie Coltrane, Hugh Laurie, Ben Elton & Stephen Fry, among others. Her best-known role is "Detective Sgt. Mo Connell" in the police series, Between the Lines (1992) (aka "Inside the Line"), filmed in 1992/1993/1994. She is a very accomplished classical actress who has acted in many theater plays (like "Look Back in Anger" that followed a world tour in 1990, with Kenneth Branagh and Emma Thompson) and some other roles in movies, as well.