Actress Kate O'Mara, known best for her role in the soap opera "Dynasty," has died at 74. She became a household name while playing Alexis Colby’s scheming sister Cassandra "Caress" Morrell. (Michael Walter/AP)

Kate O’Mara, a British actress best known for her role in the 1980s prime-time soap opera “Dynasty,” died March 30 in a nursing home in southern England. She was 74.

Her agent, Phil Belfield, confirmed the death but did not specify the nature of Ms. O’Mara’s illness.

The actress, who began her television career in the 1960s, became a household name for playing Cassandra “Caress” Morrell, sister to Joan Collins’s Alexis Colby, in “Dynasty.”

In Britain, she is often remembered for her role in “Triangle” — a soap opera set aboard a North Sea ferry that is often cited as the worst program ever on British television.

Ms. O’Mara also appeared in the original run of the British series “Doctor Who” and the BBC drama “Howards’ Way.” In the 1990s she starred in the comedy show “Absolutely Fabulous” with Joanna Lumley.

More recently she appeared in a 2012 stage adaptation of Agatha Christie’s “Death on the Nile.”

Survivors include her sister, actress Belinda Carroll.