Jill was born in Lambeth, London on April 11th 1937 and brought up in Kingston upon Thames.
Jill trained at the Italia Conti and began her theatrical career at the age of fifteen as a dancer in the chorus of a pantomime at the Grand Theatre, Halifax. She spent the next ten years singing and dancing her way through musicals and revues.
She has two sons, Sean and Adam from her first marriage to Dundee Hotelier Bill Keith. Keith was a compulsive gambler and even through her pregnancies, Jill was forced to survive almost on her own as Keith would not be able to tear himself away from his gambling. Consequently they parted company and Jill struggled on her own, to bring up her two sons in a grotty flat with no bath or hot water. Four year old Sean was forced to share a bed with his mother, whilst baby Adam was sleeping in a drawer as they had to survive on Jill’s £28 a week wage from theatre work. Jill lost contact with Keith and had no further communication with him after they had separated.
In 1959 Jill has a small role as part of the ensemble in the Paul Schofield TV film Expresso Bongo from the 1958 musical of the same name.
1960 she starred (albeit uncredited ) as a pupil in the film The Pure Hell of St Trinian’s.
In 1961, Jill's career turned towards "straight" acting, and she spent the next ten years touring the countries repertory theatres including Leicester, Dundee, Nottingham and Glasgow, her earlier work found her collaborating with another up and coming name, future television and film director Ken Roach.
In 1972 she met theatrical agent Marina Martin, who launched her television career, having already appeared in an episode of Dr Finlay’s casebook in 1970.
Further television work continued throughout the 1970’s including appearances in, Z-Cars", "Softly, Softly", "Within these Walls", "Dixon of Dock Green", "Armchair Theatre" and "General Hospital amongst others.
In 1976 The role of Letty Gaunt came up for BBC’s The Onedin Line and proved to be an important break for Jill as this was a prime time show with a good run which got her noticed. This turned into a recurring role between 1976 – 1979.
In 1980 small screen history was to be made with a new show from writer Terence Feely, entitled The Gentle Touch. The lead character was a female former police cadet who had worked her way up through the ranks in the world of policing and was now posted to London's Seven Dials police station, covering the areas of Soho and Covent Garden and was a first for a female lead character of this kind, Made at a time when there were few females in senior positions in the force, it reflected the social changes of the time, as women sought to attain the level of jobs that had previously been overly male orientated and in doing so, paved the way for future female lead roles .
Jill took the part and made it her very own as Detective Inspector Maggie Forbes. The role charted the professional and private life of DI Forbes, who had worked her way up through the ranks of the Met before arriving newly promoted to CID at Seven Dials.
In the first episode Maggie's police officer husband is shot and killed in the line of duty leaving her to juggle her career with looking after her teenage son, Steve and caring for her elderly Father. On one level it was a standard police drama but unlike The Sweeney it wasn't about punch-ups and car chases. In fact, DI Forbes was only ever seen behind the wheel of a stationary car or as a passenger because Jill Gascoine couldn't drive.
There was even the odd romantic moment for DI Forbes thrown into the mix and it all made for a massive ratings success, going out in the 9pm slot on Friday nights (except for the fifth and final series which was switched to Saturdays). For two years until 1982 Derek Thompson - who would become a British TV institution as Charlie Fairhead in Casualty - played the role of Det Sergeant Jimmy Fenton. Gascoine played the central character with a combination of sensitivity and grit, making Maggie a believable character. The Gentle Touch was a huge ratings winner, with one episode, in January 1982 drawing in over 18 million viewers and was the 5th most watched television programme that year. This show made Jill Gascoine a household name and ran for 5 series until 1984.
C.A.T.S Eyes followed shorty after, running for three series from 1985 - 1985, which saw Jill reprise her role as Maggie Forbes in a slightly more action orientated direction.
In 1987, Jill toured with the National Production of George Bernard Shaw's "CANDIDA", in which she played the title role. She also played pantomime for three years running ('85-'87), taking the part of principal boy twice.
Following this, she then appeared as Judy Schwartz in the final series of the sitcom Home to Roost (89–90) opposite John Thaw, and continued to make guest appearances on British television. She also appeared as Mrs Williams in the 1989 film King of the Wind oppositeRichard Harris and Glenda Jackson.
After a high profile career that had spanned over twenty years on British television, Jill and her second husband, actor Alfred Molina, moved to Los Angeles in the 1990s. Since moving there, Jill has made appearances on US television in series such as Northern Exposure and Touched by an Angel, as well as performing extensively in theatre.
In the 1990s she began a career as a novelist. Her first novel was Addicted (1994), about a successful television actress in her fifties who embarks on a destructive affair with a younger, half-English/half-Spanish actor in his thirties. Interestingly, Gascoine's real-life husband Alfred Molina is an English actor of Italian/Spanish descent and is 16 years her junior. This was followed by her second novel, Lilian (1995), about a woman who begins a love affair when she goes on holiday to California with her best friend.
Her third novel was Just Like A Woman (1997), which details the story of Daisy, a middle-aged woman who is being pressured by her family to have an abortion after she falls pregnant in her fifties.
Though she still lives in Los Angeles, Jill returned to the UK in 2008 to perform at the Edinburgh Festival Fringe, appearing in Colette Freedman s play Sister Cities at the Gilded Balloon Theatre.
In 1997, she was found to have kidney cancer, though the disease was detected early and she made a full recovery.
In October 2009, it was announced that Jill was joining the BBC One soap opera EastEnders. She was to play the role of Glenda Mitchell, former wife of Archie Mitchell and mother of Ronnie and Roxy, from early 2010. However, during her first day on set, she withdrew from her filming commitments, as she felt that she "lacked the right experience to film such a big continuing drama". The part was re-cast with Glynis Barber.
In June 2013, Jill publicly revealed that she has Alzheimer's disease at a Beverly Hills gala which was set up to raise money to fight the disease.