Career
She played the part of Vicki in 38 episodes of Doctor Who from 2 January to 6 November 1965, starring alongside the original Doctor, William Hartnell. Over 40 years later, she reprised the role in several Big Finish Productions Doctor Who audio plays. After leaving Doctor Who, O'Brien found it difficult to find acting work on television, and worked as a supply teacher.
Her next role was in the theatre, where she appeared in an Oxford Playhouse production of Volpone with Leo McKern and Leonard Rossiter. She had a recurring role as Morgan in The Legend of King Arthur (1979) and unit general manager Elizabeth Straker in the second season of Casualty (1987). She made numerous guest appearances in The Duchess of Duke Street ("Trouble and Strife"), Taggart ("Forbidden Fruit"), Cracker ("The Big Crunch"), A Touch of Frost ("Private Lives") and Heartbeat.
She appeared also in an early episode of Jonathan Creek, playing Kirsten Holiday in the episode 'Jack in the Box'. In the 1970s she directed a production of Brecht's Caucasian Chalk Circle at Ottawa University, Canada. The 1980s saw her teaching acting workshops in the USA. She also made a rare film appearance in the comedy She'll Be Wearing Pink Pyjamas in 1985 opposite Julie Walters.
She was awarded the Time Out's Critic's Choice for her production of Mike English's Getting In in 1986. O'Brien has also written seven detective novels: Close-Up on Death (1989), Deadly Reflection (1993), Mask of Betrayal (1998), Dead Innocent (1999), Revenge (2001) Unauthorised Departure (2003) and Every Step You Take (2004). All featuring the character of Detective Inspector John Bright.
O'Brien was born in Liverpool, Lancashire and attended Notre Dame School in Liverpool as well as the Central School of Speech and Drama in London.
