After completing her education at the WDADA, Cornwell began her career as an actress, making her debut for
Richard Cottrell's
Cambridge Theatre Company in November 1971 as Miss Brewster in
Arthur Wing Pinero's ''
Trelawny of the 'Wells'''. She remained a member of the Bristol Old Vic Company through to 1975, playing a broad range of roles from Kate Hotspur in
Shakespeare's
Henry IV to Becky in
Sam Shepard's
The Tooth of Crime and
Queen Elizabeth I in
Robert Bolt's
Vivat! Vivat Regina!. Particular critical attention was given to her portrayal of
Florence Nightingale in the company's 1973 revival of
Edward Bond's controversial play
Early Morning in which the company restored previously legally banned
lesbian love scenes between Nightingale and
Queen Victoria; the latter part played by
Elizabeth Power. While working at the Bristol Old Vic, Cornwell made her screen debut in the small role of Sally Potter in the 1974 musical film
Stardust. In 1975 she performed the role of Cecily in
Oscar Wilde's
The Importance of Being Earnest at the
Greenwich Theatre. In 1976 Cornwell rose to fame for her portrayal of the drug addicted rock star Anna Wynd in the
BAFTA Award winning television drama
Rock Follies (1976) in which she was part of a musical trio which also included
Julie Covington as Dee and
Rula Lenska as Q. The music the three women recorded for this television drama was released as a
soundtrack album which reached number 1 on the
UK Albums Chart. She worked extensively both in the
West End and at fringe venues, and appeared in the United States in several productions, including
Richard III and
An Enemy of the People opposite Sir
Ian McKellen,
Athol Fugard's
The Road to Mecca, Terence McNally's
Master Class,
Stephen Sondheim's
A Little Night Music (San Francisco Bay Critics' Award), and
Alan Bennett's
The History Boys at the
Ahmanson Theatre in Los Angeles. In a return to staged Shakespeare, in Summer 2016 she was the Chorus in the
Regent's Park production of
Henry V. Among her film appearances were roles in
Stardust (1974),
The Brute (1977),
The Krays (1990),
The Russia House (1990),
White Hunter Black Heart (1990),
The Saint (1997),
Ghosts of Mars (2001) and
Dead Space: Aftermath (voiceover, 2010). Cornwell worked extensively on television including series lead roles in
Rock Follies (1976–77) and
No Excuses (1983), and appearances in ''
The Men's Room, The Governor, Shalom Salaam
, Shoestring, Lovejoy, Love Hurts, Where the Heart Is, A Touch of Frost, Silent Witness, The Mentalist, Dressing for Breakfast, Capital City, The West Wing, Casualty, The Practice, New Tricks, Toast of London, and Midsomer Murders'', among other television programmes in Britain and the United States. She taught at the
University of Southern California School of Dramatic Arts from 2004 to 2012, and returned to resume her acting career in the UK in June 2012. Cornwell won a libel action against the journalist
Nina Myskow and
The Sunday People in December 1985. A jury at the
High Court awarded her £10,000 in damages after Myskow, in an article for the newspaper, had referred to Cornwell as someone unattractive, middle-aged and whose "bum is too big". The verdict was upheld on appeal, but Cornwell ended up £70,000 out of pocket from legal costs. However, the award for damages was raised to £11,500. ==Personal life==