Following graduation from the London School of Economics, Sylvia Thamm joined Polytechnic Films as a secretary, where she met editor/director Gerry Anderson. When Anderson and his colleague Arthur Provis created AP Films following the collapse of Polytechnic in 1957, Sylvia joined them along with colleagues John Read and Reginald E. 'Reg' Hill. She became Anderson's second wife shortly after, in 1960, and became more involved in production duties.
The creative partnership with Gerry Anderson concluded when their marriage broke down during the production of the first series of Space: 1999 in 1975; Gerry announced his intention to separate on the evening of the wrap party, following which Sylvia severed her ties with the production company.
It is widely believed (and erroneously reported on other websites, including the IMDB) that Sylvia was involved in the production of the cult mid-1970s television series Star Maidens. This is, in large part, due to the striking design of the programme, reminiscent of UFO and Space: 1999. However, as was the case with these Anderson productions, the look of Star Maidens was actually due to production designer Keith Wilson. A large number of the AP Films/Century 21 alumni worked on Star Maidens, but Sylvia Anderson was not among them.
In 1994, Sylvia reprised her role as Lady Penelope on one episode of Absolutely Fabulous. Indeed, nowadays Sylvia is widely recognised as Lady Penelope's alter-ego in lieu of virtually any of her other achievements. Whilst Gerry Anderson has continued developing and producing since their separation Sylvia has, until recently, acted as the UK representative for HBO, scouting for new talent. Her autobiography Yes M'Lady was published in 1996, and republished as My FAB Years in 2007, with new material bringing it up to date with the latest development in her life, including her role as a consultant on Working Title's almost universally panned Thunderbirds (2004) movie.