[7] She became interested in acting after getting a place in the choir, at age 14, for the world premiere of the finalised version of Joseph and the Amazing Technicolor Dreamcoat, presented in Leicester in 1974.
[1][8] Simon later appeared in pantomimes before finishing secondary school,[7][1][5] and played Martha in a 1976 production of The Miracle Worker directed by Michael Bogdanov at the Leicester Haymarket Theatre.
[4] Alan Rickman, who was in the production of Joseph and the Amazing Technicolor Dreamcoat, encouraged Simon to apply for the Central School of Speech and Drama in London and she was accepted.
[9][10] Simon won the part of Dayna Mellanby in the BBC 1 television sci-fi series Blake's 7 after being talent-spotted while still at the Central School of Speech and Drama.
[15] Andrew Muir, author of a book about the series, felt that Simon provided "energy, vitality, innocence, danger, and a real physical presence" to the character.
[11] After taking part in a reading of Salvation Now by Snoo Wilson in 1982,[23][24] she was cast as one of the three "weird sisters" in Macbeth alongside Kathy Behean and Lesley Sharp later that year.
[27] In 1997, Simon told academic Alison Oddey that working with Michael Gambon and, particularly, Helen Mirren on Antony and Cleopatra provided an early influence on her career.
[36] Jami Rogers, in her book British Black and Asian Shakespeareans (2022) commented that in Kyle's production, where the women were dressed in Belle Époque-style silk dresses, Rosaline's clothing "immediately marked her as a woman of high status ... For the first time on a major British stage, an African-Caribbean woman portrayed an intelligent, witty and strong leading Shakespearean character.
[40] She told Veronica Groocock, author of Women Mean Business (1988), that sexism had been as much of an issue as racism in her career, although the problem reduced as she gained larger roles.
[41] Nine years later, she expressed her dissatisfaction with the lack of good roles for women, which she ascribed to the industry being male-dominated and complained that, "I think that we've seen more and more trivialising of actresses, requiring them to look gorgeous and take their top off at some point.
[50] Financial Times critic Martin Hoyle wrote of the Barbican production that Simon "has transformed her voice, both timbre and enunciation .... Incisive, vocally varied, though slightly lacking the full weight for the early emotional climaxes, she gives the best performance I have seen from her, dignified and touching.
"[51] In The Times in 1991, Benedict Nightingale opined that by casting Simon as Isabella and Rosaline, and Hugh Quarshie in other plays, the RSC had been "launching two performers of huge potential".
The drama and theatre scholar Lynette Goddard argued that despite the RSC's inclusive policy, black women actors still had limited opportunities to progress, "which makes Josette Simon's case all the more compelling".
The Financial Times reviewer wrote that Simon spoke "Titania's lines with an almost jazz musicality, dances, moves, and stands with compelling power.
Rick Groen of The Globe and Mail wrote that Simon's "riveting performance ... carries the picture" for the first part, but felt that from the second act onward, the film descended into histrionics.
[72] In the San Francisco Chronicle, Judy Stone praised Simon's performance as Joanna, commenting that "she displays a quality of grace all too rare in today's films".
[70] The 1992 television play Bitter Harvest had Simon in the lead role, as a woman who has gone missing after travelling to the Dominican Republic as an aid worker and whose parents go there in search of her.
The English Literature scholar Claire Tylee considered that Simon's character was a "credible protagonist", but the film was adversely affected by a mismatch between its thriller and family plotlines.
After Simon had already accepted the leading role based on an outline the producer Charles Pattinson pitched, the scriptwriter Winsome Pinnock altered the storyline to include tensions in the mixed-race family.
[75] The Newcastle Journal reviewer Norman Davison commented that the two lead actors "invested the roles with the sort of power that all La Plante women seem to have and the men were all the wimps".
[79] Simon has played senior police officers in Silent Witness (1998),[80] Minder (2009),[81] and Broadchurch (2017),[80] and has been cast as Chief Commissioner Camberwell in Anansi Boys, which was in production as of May 2022.