She is known for portraying the role of Pat Butcher in the BBC soap opera EastEnders from 12 June 1986 until 1 January 2012, with a guest appearance in May 2016, thereby becoming one of the programme's longest-serving cast members.

[3] Shortly after St Clement's birth in 1942, her mother died of tuberculosis, and she was put into foster care when her father remarried.

"[5] St Clement's father rose to become the managing director of a toy manufacturer in London and was married five times.

[6] Her acting career began in the 1970s, when she joined a small theatre company and she went on to have minor roles in programmes such as The Onedin Line (1972) and Follyfoot (1972).

[9] Subsequent television credits have included: Van der Valk (1977); A Horseman Riding By as Meg Potter (1978); Emmerdale Farm (1980) as Mrs. Anne Eckersley; Thomas & Sarah (1980); Enemy at the Door (1978; 1980); Play For Today (1980); Minder (1980); Shoestring (1980); Dangerous Davies (1981); Angels (1981); as Frau Bodelschwingh in Private Schulz (1981); The Chinese Detective (1982); The Tripods (1984); Bottle Boys (1984); and Hammer House of Mystery and Suspense (1986).

She has also appeared in films, including roles in Doomwatch (1972), Hedda (1975), The Bunker (1981), Scrubbers (1983) and Hitler's SS: Portrait in Evil (1985).

St Clement initially had reservations about committing to the role, commenting: "I couldn't envisage how this character, who creates absolute havoc everywhere she goes and is not at home with herself or with anybody else in the Square, could possibly fit in".

[citation needed] She featured in a multitude of high-profile storylines, which included a total four marriages (two of which had happened before the show's launch) — most notably to Frank Butcher (played by Mike Reid) – numerous affairs, feuds and a spell in prison for drink-driving (which led to a pedestrian dying).

Of her departure St Clement said "I have enjoyed 25 and a half wonderful years in EastEnders creating the character of Pat but feel it's time to hang up her earrings.

She has since been associated with EastEnders and on 14 November 2014, St Clement reprised the role of Pat for a short stint for Children in Need after Ian Beale (Adam Woodyatt) knocks his head and sees the deceased women in his life.

In February 2015, St Clement, alongside Windsor, took part in EastEnders: Back to Ours, which celebrated 30 years of the soap opera.

[14] On 17 May 2016, she reappeared as Pat, again playing opposite Windsor, for a few minutes as an imagined figure in conversation with the terminally ill Peggy Mitchell.

[16] St Clement would appear as "grumpy patient" Sally Hodge who "makes life hell" for charge nurse Charlie Fairhead (Derek Thompson) because she is "distrustful" of him.

In November 2017, St Clement appeared on Gone to Pot: American Road Trip in which five celebrities (mainly older aged) go across California and Colorado to find out how cannabis can be used medicinally and how it would affect the UK if it was legalised.

[3] St Clement has been the focus of much media criticism regarding her weight over the years, which earned her character the nickname "Fat Pat".