Mary Tamm: Actress who made her name as the Time lady Romana in 'Doctor Who'

She only took thepart of Romanawhen assuredshe would be theintellectual equalof the Doctor

Playing the first incarnation of the Time Lord's companion Romana in Doctor Who brought Mary Tamm long-lasting fame, even though she left the role after just one series (1978-79). Her haughty but cool character was seen helping the fourth Doctor (Tom Baker) in a quest to locate the Key to Time, a powerful artefact used by the Guardians of Time to maintain control over universal order and chaos. Tamm had initially been reluctant to take on the part, until being assured that Romana (full name Romanadvoratrelundar) would be from the Time Lord's own race and – in the vein of a previous companion, the scientist Liz Shaw (played by Caroline John, who died in June) – an intellectual equal.

"It wasn't that she was just going to be a companion or even an assistant – she was a Time Lady," explained Tamm in a 2007 interview. "They said, 'She's going to be just as powerful as the Doctor.' It did work for a while, but it was only a half-hour format and you've got to have somebody who's explaining what's going on to the audience, so inevitably I ended up saying, 'Oh, what's that, Doctor? Why, Doctor?' After 26 episodes, I thought, 'It's not going to go any further.' I'd had enough by then and I decided to leave after that one series." The actress was then pregnant with her daughter, Lauren, and recommended Lalla Ward to play the regenerated second incarnation of Romana.

Tamm was born in Dewsbury, West Yorkshire, to parents who fled Estonia in 1945 after four of her father's brothers had died in Stalin's labour camps, She was brought up in Bradford's Estonian community, spoke the language at home and attended one of its schools on Saturdays.

At the age of 11, she won a scholarship to Bradford Girls' Grammar School and joined the Civic Theatre, having been introduced to the arts by her mother, a Russian-born opera singer who was a vocal teacher in the city. Tamm trained at Rada (1968-71) then spent a year with the Birmingham Repertory Theatre, making her professional début in the musical Good Time Johnny (1971-22) alongside Ronnie Barker, until he had to pull out for an operation on his vocal chords.

In 1973, after making her television début with a one-off part in the police series Hunter's Walk (1973), Tamm appeared in three episodes of Coronation Street as Pauline – known as Polly – the daughter-in-law Stan and Hilda Ogden never knew they had until they tracked their son Trevor down to Chesterfield, where the couple lived with their equally secret baby son. Trevor had apparently been ashamed of his parents and told Polly they were dead. Between scenes, Tamm enjoyed playing bridge on set with Doris Speed, who acted the Rovers Return landlady Annie Walker.

She was also cast in the horror film Tales That Witness Madness (1973) as Ginny, sacrificed by her literary agent mother (Kim Novak) as the flesh of a virgin that guarantees a client passage to Heaven. Then came a film role that gave Tamm international exposure, as Sigi, unaware of the motives behind her boyfriend's search for a Nazi war criminal, in The Odessa File, the 1974 adaptation of Frederick Forsyth's thriller, starring Jon Voight as the journalist ultimately seeking revenge.

After her run in Doctor Who, Tamm was seen on television as Jill Fraser in the spy thriller The Assassination Run (1980) and its sequel, The Treachery Game (1981); Blanche Ingram, the callous socialite briefly courted by Mr Rochester in an attempt to make the heroine jealous, in Jane Eyre (1983); and Jennifer Reynoldston in the David Nobbs-written sitcom The Hello Goodbye Man (1984). She had a two-year run (1993-95) in the soap opera Brookside as Penny Crosbie, the widow of a cheating MP who committed suicide after newspaper revelations that he had been involved with a prostitute.

The later years of Tamm's career were spent mostly in one-off character roles on television, although in the drama series Paradise Heights (2002) she played Yvonne Edwards, elegant wife of Jack, the rival who loaned money to a struggling warehouse business run by three brothers and remains a constant threat. She also returned to soap opera, first in one episode of Coronation Street as Diana Black (2002), settling her dead mother's Canine Weekly bill at The Kabin and re-homing her shiatsu with Rita Sullivan.

In 2009 she spent a week in EastEnders as Orlenda, a Russian befriended and taken in by Charlie Slater (Derek Martin) but eventually confessing to being a con artist who could not go through with fleecing him. Tamm said she was cast in the role because of her mother being Russian – a fact recalled by the director, who had worked with her on Brookside.

On stage, Tamm made many appearances in regional productions and national stage tours, as well as playing Rhoda Daws in Cards on the Table in the West End (Vaudeville Theatre, 1981). She regularly attended Doctor Who conventions in Britain and the US, reprised Romana in a series of audio releases (2005-12), wrote short stories for women's magazines and translated Estonian plays into English.

Tamm's autobiography, First Generation (referring to both Romana and her own experience as an Estonian in Britain), was published in 2009. A second volume, titled Second Generation, was unfinished at the time of her death, after an 18-month fight against cancer.

Marie Tamm (Mary Tamm), actress and writer: born Dewsbury, West Yorkshire 22 March 1950; married 1978 Marcus Ringrose (one daughter); died London 26 July 2012.