Angharad Rees: Actress best known for her role as the headstrong Demelza in Poldark

She also ran a jewellery design business; her pieces were used in ‘Elizabeth: The Golden Age’

The period drama has long been a staple of British television and has proved just as popular, not only in other English-speaking countries but also across continental Europe, bringing much-needed overseas revenue to the BBC and ITV companies. Long before Downton Abbey, viewers were entranced by Poldark, the 18th-century Cornish saga which starred Robin Ellis as the eponymous army officer turned tin-mine owner, and Angharad Rees as Demelza, the headstrong servant girl he eventually marries.

Between 1975 and 1977, up to 15m viewers tuned to BBC 1 on Sunday evenings for the latest of the 29 episodes based on Winston Graham's historical novels. With her auburn tresses, wench bonnets and the strong West Country accent she felt the character needed, Rees made her portrayal of the vivacious Demelza memorable. Her wilfulness resonated with women of all ages and contributed to the series' popularity as much as Ellis's brooding looks.

"It was a rip-roaring yarn, with wonderful characters," she said. "Everything was heightened. Living at that time, it needed to be. You couldn't stroll through Poldark." Indeed, when released on video in the 1990s, Poldark became the BBC's best-selling costume drama until the 1995 version of Pride and Prejudice.

One of four siblings born to the eminent Welsh psychiatrist Professor Linford Rees and his wife Catherine Thomas, she spent her early childhood in Cardiff before returning to London in the mid-1950s. She struggled with dyslexia, but made the most of opportunities to study in Paris and Madrid in her late teens. Set on acting, she won a scholarship to the Rose Bruford college in Surrey and subsequently worked in regional repertory.

In 1968, she made her television debut as the parlour maid in an adaptation of the Shaw play Man And Superman featuring Maggie Smith and Eric Porter, and also appeared alongside Patrick Macnee, Linda Thorson and Ian Ogilvy in "They Keep Killing Steed", one of the more left-field episodes of The Avengers series, directed by Robert Fuest. In 1970, she was in a TV movie version of Jane Eyre with Susannah York in the title role, which brought her to Hammer's attention.

The British horror powerhouse was attempting to reinvent the genre for the 1970s with movies like Countess Dracula and Dr Jekyll And Sister Hyde. In 1971, they cast Rees as Jack The Ripper's daughter in Peter Sasdy's grand guignol Hands Of The Ripper. Featuring dialogue gems like "Her hands – they weren't her hands at all!" and "You can't cure Jack The Ripper – and that's who she is!" uttered by the very actorish Derek Godfrey to Porter, a doctor who thinks he can cure her, Hands Of The Ripper contrasted the heroine's doe-eyed innocence with the gory way in which she dispatched Dora Bryan, Marjie Lawrence and Lynda Baron. The climactic scene at St Paul's Cathedral cemented the film's cult status among connoisseurs of gothic horror.

Her subsequent career combined highbrow projects, including her portrayals of the schoolteacher Gossamer Beynon in Andrew Sinclair's film of Under Milk Wood (1972) starring Richard Burton, Elizabeth Taylor and Peter O'Toole, and of Winston Churchill's daughter Sarah in The Gathering Storm (1974), with Burton as the prime minister, as well as more lowbrow fare such as the action series The Protectors and the sitcom Doctor in Charge. In 1974, she was nominated for a best newcomer award for her role opposite Keith Michell in the dreamlike film Moments.

Poldark enabled Rees to move away from the "girlfriend" parts and show her mettle among a cast which included Jill Townsend as Elizabeth, the hero's former fiancée, who first marries his cousin and is then betrothed to his nemesis, the villainous banker and land owner Sir George Warleggan, played by Ralph Bates. The demanding schedule took in several weeks' shooting on location in Cornwall, a departure from previous set-bound dramas like Upstairs, Downstairs.

Now a star name, Rees guested in The Morecambe and Wise Christmas Show in 1977 – one of the 25 most watched programmes in British television history – and played Celia alongside Helen Mirren's Rosalind in a 1978 TV production of As You Like It filmed at Glamis Castle in Scotland.

The chemistry between Rees and Ellis had been such a strong ingredient of Poldark's success that they were reunited in the 1980 TV film The Curse Of King Tut's Tomb. However, an attempt by HTV, the Wales and West of England ITV company, to revive the Poldark franchise in 1995 and film the novels Graham had written in the intervening years, floundered when Rees and Ellis were told they would only receive half the £60,000 fee they had been offered originally and they pulled out. A pilot, with John Bowe and Mel Martin in their stead, was filmed, but it aired to disappointing ratings in 1996. Members of the Poldark Appreciation Society were so incensed that they donned 18th century garb and picketed HTV's headquarters in Bristol.

Rees also enjoyed an extensive theatre and radio career but she spent most of the 1980s looking after her two sons by her first husband, the actor Christopher Cazenove – of Dynasty fame – with whom she also filmed Nescafé commercials. She returned in the London Weekend Television sitcom Close To Home (1989-90) as the remarried ex-wife of a vet played by Paul Nicholas, and also appeared in the second series of Trainer (1992), set in the world of horse racing.

Following her divorce from Cazenove in 1994, and the death of their eldest son, Linford, in a car accident in 1999, she gave up acting and concentrated on running her jewellery design business in Knightsbridge. In 2007, her distinctive pieces were featured in the film Elizabeth: The Golden Age, starring Cate Blanchett.

Rees was an honorary fellow of the Royal Welsh College of Music and Drama and was appointed CBE in 2004. She died of pancreatic cancer.

Angharad Mary Rees, actress and jewellery designer: born London 16 July 1949; married 1973 Christopher Cazenove (divorced 1994; one son, and one son deceased), 2005 David McAlpine; died London 21 July 2012.