Janet Fielding (born Janet Mahoney in Brisbane, Queensland, Australia) played companion Tegan Jovanka from Logopolis to Resurrection of the Daleks, with a cameo appearance in the role in the conclusion of The Caves of Androzani.
Fielding played the part between 1981 and 1984. She made a guest appearance on Jim'll Fix It in a Doctor Who related sketch alongside Colin Baker's Sixth Doctor in 1985 (A Fix with Sontarans). A featurette included in the 2010 DVD release of Time and the Rani reveals that she participated in the auditions for the Seventh Doctor, portraying a villain opposite several hopefuls, including Sylvester McCoy.
She is now a theatrical agent — she represented Paul McGann when he first took the role of the Eighth Doctor — and has been an outspoken advocate of greater women's participation in film and television, acting as an administrator for the pressure group Women in Film and Television.
In 1982, Fielding married Daily Mirror foreign editor Nicholas "Nick" Davies, notable for later allegations of being an arms dealer and Mossad agent. They divorced in 1991. Their wedding coincided with the filming of Mawdryn Undead, and a gag publicity portrait at the time showed Fielding in her bridal gown, wearing the make-up used for the scene in which Tegan and Nyssa are aged rapidly by physical contact with Mawdryn. 
Despite distancing herself from Doctor Who for many years and being vocal in her criticisms of the program, Fielding returned to the role of Tegan for the Big Finish Productions audio drama titled The Gathering, released in 2006, once again alongside Peter Davison as the Fifth Doctor. In 2010 she began recording a series of Big Finish adventures that reunited her with not only Davison, but her former co-stars Sarah Sutton and Mark Strickson.