Sian was born in Stratford-on-Avon, a fitting origin for a stage performer, given her connection to the world of theatre. Interestingly, she is the sister of fellow actress Sara Mair-Thomas, which likely influenced her early exposure to the performing arts.
Sian's childhood was marked by a stint in Canada, a significant experience that would shape her perspective and inform her artistic endeavors. Following her graduation from the Central School of Speech and Drama, she embarked on a year-long repertory journey, honing her craft and developing her skills.
A pivotal moment in her career arrived when she spent two years at the Glasgow Citizens' Theatre, a period she describes as one of the happiest times of her life. This formative experience laid the foundation for her subsequent success, as she went on to make her debut as "Katarina" in the Royal Shakespeare Company's production of "The Taming of the Shrew".
Sian's impressive stage credits include collaborations with leading theatre groups, such as the National Theatre, where she met her partner, the director and writer Tony Harrison. One of her most notable roles was alongside Madonna in the American performer's West End debut in "Up For Grabs". While some critics may have perceived her as stealing the spotlight, Sian herself recalls the experience as enjoyable and would welcome the opportunity to work with Madonna again.
In addition to her stage work, Sian has appeared in various television mystery thrillers, including "Midsomer Murders" (1997),"Taggart" (1983),and "The Bill" (1984). Like many British actors, she has navigated the familiar terrain of these popular programs, showcasing her versatility and range as a performer.