Born: August 10, 1939; Died: March 30, 2014

Kate O'Mara, who has died aged 74, was an actress who appeared in what could almost qualify as a complete list of British cult television series. She popped up in Danger Man, Z-Cars, The Champions, The Persuaders!, Department S, Jason King, The Avengers, The Saint, Return of the Saint and a host of others.

Her big screen career as a young actress was largely in Hammer horror and similar melodramas, none especially distinguished, but throughout her working life she also retained a strong commitment to serious theatre, founding her own company, and taking on the classic repertoire, ranging from Shakespeare to Wilde and Sheridan to Albee.

On television she produced a memorable turn as the Rani in Doctor Who, appearing as the villain in two storylines, opposite Colin Baker (the sixth Doctor) and in the opening story for his successor, Sylvester McCoy. She reprised this role, as a renegade Time Lord exiled from Gallifrey, in a Children in Need special for the 30th anniversary of Doctor Who in 1993.

O'Mara was, however, associated first and foremost with roles as dominant women or femmes fatales in soap operas such as The Brothers (1975-76), about a road haulage empire; Triangle (1981-82), about a North Sea Ferry empire; Howards' Way (1989-90), about a yacht-building empire; the revival of Crossroads (2003), about a West Midlands motel empire; and - the role for which she was best-known internationally - as Caress Morrell in Dynasty (1986), about a Colorado oil empire.

With her feline features - she was possessed of cheekbones of practically Pythagorean angularity - it was perhaps inevitable that O'Mara should, as a young woman, have been cast as a vamp and in her later career as a hard-faced bitch. She accepted this rather unfair typecasting stoically. "I would like to be where Diana Rigg or Judi Dench is," she said, "but I expect it is as good as it is going to get."

She was born Frances Carroll in Leicester, the daughter of John Carroll, a flying instructor with the RAF, and his wife Hazel Bainbridge, an actress. Frances and her sister, the actress Belinda Carroll, were both encouraged to perform from an early age and she was sent to board at the Aida Foster Stage School in London.

She then went to art school, but the lure of the stage eventually took her back to acting, and she made her professional debut in 1964, as Jessica in The Merchant of Venice, with a company which took performances of Shakespeare to schools.

She almost immediately found herself with television roles, appearing in two episodes of the crime drama No Hiding Place, playing a student vet in the short-lived Anglia soap Weavers Green (1966), and landing guest appearances on Adam Adamant Lives! and The Troubleshooters (both 1967).

In 1968, she appeared alongside Peter Cushing in Corruption, a horror film set in Swinging London which promoted itself by refusing to admit unaccompanied women into the cinema, and which subsequently gained cult status as a high watermark in unintentional camp.

Her other forays on to the big screen were similarly specialised tastes: the Shavian comedy Great Catherine (1968); Roy Ward Baker's The Vampire Lovers (1970), with its then-daring overtones of lesbianism; and, the same year, The Horror of Frankenstein, with Ralph Bates. Both were Hammer productions during the period when the studio seemed unsure whether it was turning out straight horror films or parodies of them.

But, if her film career enjoyed mixed success, O'Mara was becoming a fixture on highly successful prime-time television dramas, and continued to work in serious theatre, playing in Shakespeare, Shaw and Coward in the West End and leading provincial theatres such as the Bristol Old Vic through the 1970s.

The Brothers, a sort of road-haulage antecedent of Howards' Way, helped to make her a household name. By the mid-Seventies she was making cameo appearances on Morecambe and Wise (as Kate O'Mata Hari) and in The Two Ronnies.

In 1981, she took on the part of Katherine Laker in Triangle, a twice-weekly soap once described as "the most mockable British television ever produced". It was set on a ferry which sailed between the glamorous settings of Felixstowe, Gothenburg and Amsterdam (hence the title).

The opening episode showed Miss O'Mara sunbathing topless on the deck, though the North Sea's usual weather conditions were clearly visible in the background. Relentlessly sent up (especially by Terry Wogan on his radio breakfast show) it nonetheless lasted three seasons.

Howards' Way, in which she played Laura Wilde in 26 episodes, was on much the same level although, unlike Triangle, remarkably popular.

But the acme of her career playing bitchy powerful characters in prime-time melodrama was undoubtedly Dynasty, in which she played the sister of Alexis Carrington, a character whom Joan Collins had already established as the last word in scheming soap villainesses.

Her television appearances continued, though they tended to be as self-conscious cameos, but she devoted herself increasingly to theatre.

She produced and directed as well as acting, and the British Actors' Theatre Company toured widely. She was married and divorced three times, always to other actors.She had a son, Chris Linde, who was given up for adoption, and later sold his story to the newspapers after failing to connect with his mother in later life. She was devastated when another son, Dickon Young, who had worked as a stage manager and set designer for her theatre company and lived with her, committed suicide in 2012 after suffering mental problems following an accident.

She wrote two novels and two autobiographies. Last year, she appeared in An Evening with Kate O'Mara, a one-woman show in London's West End.

She latterly lived near Chard, in Somerset and died yesterday at a Sussex nursing home after a short illness.