Cracknell was born in 1925 in Maitland, New South Wales to Charles and Winifred Cracknell. When she was four years old, the family moved to Sydney. She was educated at North Sydney Girls High School and, after graduating, worked at the Ku-ring-gai Council as a clerk. At 17 she was taken to the theatre by a friend. She immediately wanted to become an actress and joined the Modern Theatre Players drama school.
Cracknell's first acting jobs were in radio. By 1946, she was performing five episodes of radio plays a week. She also performed on stage with the Independent Theatre Company and the Mercury Theatre. In 1948, she joined the John Alden Company and had roles in King Lear, Measure for Measure and The Tempest. In 1952, at the age of 27, she left Australia to work in London for two years.
Cracknell appeared in many Australian film and TV productions, including the 1973 award-winning ABC-TV dramatisation of Ethel Turner's Australian children's classic Seven Little Australians. One of her first TV roles was in Reflections in Dark Glasses, a one-off drama broadcast in 1960.
Cracknell is most well known for her role in the ABC television series Mother and Son. Written by Geoffrey Atherden and based on the writer's own family experience, Mother and Son first screened on 16 January 1984; it continued for six seasons for over a decade and is often repeated. Cracknell played an elderly woman, Maggie Beare, who was slowly becoming senile. She was cared for by her long-suffering younger son Arthur (Garry McDonald), to whom she was often indifferent but on whom she was also dependent and whom she often cynically played off against her self-centred older son Robert (Henri Szeps) and daughter-in-law Liz (played by Judy Morris).
Cracknell appeared in over 20 films and television series, including Play School (throughout the 1960s), The Chant of Jimmie Blacksmith (1978), the 1983 miniseries The Dismissal (playing Margaret Whitlam) and A Country Practice (two episodes in 1984). She also appeared in the classic Australian film "Smiley Gets a Gun" with Chips Rafferty in the 1950s.
Cracknell acted for most of the major Australian theatre companies, especially the Sydney Theatre Company. As well as other stage roles, she appeared in the stage production of The Importance of Being Earnest as Lady Bracknell. The production was so popular that it was an "ongoing" stage production from 1988 to 1992 and was televised by the ABC. She was also Patron of the Australian Theatre for Young People.
Cracknell married Eric Phillips on 25 June 1957 and they had three children, Anna, Jane and Jonathan. Unlike many women of the time, she did not retire, but continued to act.
In 1997 Cracknell published her autobiography, A Biased Memoir, which was a best seller in Australia. In 2000 she published her memoir, Journey from Venice, which related how she and her husband, Eric Phillips, were visiting Venice when he had a paralysing stroke; she did not speak a word of Italian but she had to organise medical treatment for him and have him returned to Australia in the face of significant obstacles. He later died in a Sydney hospital.
Cracknell died of a respiratory illness in a Sydney nursing home on 13 May 2002, aged 76, shortly after a visit from her children, Anna Jeffery, Jane Moore and Jonathan Phillips. She was also survived by seven grandchildren. Paul McDermott's film The Scree, which was released in 2004, featured Cracknell's narration.
In 1980, Cracknell was appointed a Member of the Order of Australia (AM). In 1998, the National Trust of Australia named her one of "100 National Living Treasures". She also received honorary doctorates from the University of Sydney. and the Queensland University of Technology. In 2001 she received the JC Williamson Award for her life's work in live theatre.
In 2001, Cracknell was awarded the TV Week Logie Hall of Fame for her services to Australian television. Her appearance at the ceremony was the last before her death. She was the first Logie Hall of Fame recipient who has appeared on a TV show which also won the Logie Hall of Fame (Play School, awarded in 2006), the second being Noni Hazelhurst (having been inducted in 2016).
Logie Awards she won:1993: Most Outstanding Actress
1994: Most Outstanding Actress
1994: Most Popular Comedy Personality
2001: TV Week Logie Hall of Fame
In 1992, Cracknell was nominated for the ARIA Award for Best Children's Album for Paul Gallico's The Snow Goose.