Jenny Tomasin, a British actress forever known to hundreds of millions of television viewers as the clumsy, disheveled, Valentino-obsessed kitchen maid Ruby Finch in “Upstairs, Downstairs,” has died at her home in London.

She died Jan. 3 of hypertensive heart disease, according to the coroner’s office in her neighborhood. She was 73, according to the membership records officer for the actor’s union Equity in Great Britain. Other reference guides put her age at 75. She had no immediate survivors, delaying confirmation of her death.

“Upstairs, Downstairs,” one of the most beloved and literate television dramas of all time, chronicled the decline of a British aristocratic family and the fate of their servants from the Edwardian era through World War I, the Jazz Age and the stock market crash of 1929.

The program was produced between 1970 and 1975, drew audiences worldwide and has endured in public television reruns. It had a direct influence on films including Robert Altman’s “Gosford Park” (2001) and shows such as “Downton Abbey,” now airing on public television.

“Upstairs, Downstairs” was celebrated for its finely drawn portrait of the British class system — including the hierarchy of servants. Although Conservative politician Richard Bellamy (David Langton) was the master upstairs at the fictional 165 Eaton Place in London’s Belgravia neighborhood, downstairs was the domain of the formidable head butler Hudson (Gordon Jackson) and the tyrannical cook Mrs. Bridges (Angela Baddeley).

Ruby — gray-faced, thatchy-haired and hopeless in the kitchen — was distinctly at the bottom of the social ladder. Few who saw the series will fail to remember Mrs. Bridges taking pity on the “poor girl” but also erupting in her trademark bellow, “Roo-BEEE!”

Ms. Tomasin joined the show in 1972 after another scullery maid committed suicide. During World War I, the maladroit Ruby leaves for a short-lived job in a munitions factory. Having left Eaton Place proud of her independence, Ruby returns blackened when the plant explodes.

In interviews, Ms. Tomasin said she was devastated when her career plummeted after the success of “Upstairs, Downstairs.” She appeared in small roles in London’s West End and in touring productions.

There was a melancholy consistency to her sporadic television work. She twice appeared on the British soap opera “Emmerdale” — in the early 1980s and in the mid-2000s — and each time, her character was killed off.

Jenny Tomasin was born in Leeds, in northern England, on March 22, 1938, according to the actors’ union. Other reference works say she was born on Nov. 30, 1936, with no explanation for the discrepancy of day, month and year.

She said her parents, who were working-class, were unsupportive of her ambition to act. She had a middling career until “Upstairs, Downstairs” producer John Hawkesworth exclaimed on seeing her photo in a British casting directory, “That’s the face!”

Ms. Tomasin appeared in reunion documentaries of “Upstairs, Downstairs,” often noting with mixed feelings how the show affected her life.

“I had to wear these drab outfits and no makeup,” she said in a 2002 documentary, according to the London Independent. “There was one particular incident when I was out with my boyfriend for a meal. I was feeling sexy and attractive, and suddenly somebody yelled out, ‘Oh, look, there’s Ruby!’ I looked at my boyfriend and said, ‘I don’t want to stay here.’ It just felt awful.”

Staff writer Emily Langer contributed to this report.