Lively and attractive, Sybil Williams had a beautiful voice and a good sense of humour. Her father had been a mining official in South Wales, where most of Burton’s male relations had worked in the pits.

As Burton’s career took off, the couple moved to Switzerland in 1957, buying a house overlooking Lake Geneva and calling it Pays de Galles. Their first daughter, Kate, now a successful actress, was born there the same year and a second daughter, Jessica, followed in 1959.

Sybil provided Burton with a haven from the pressures of celebrity, both because she connected him to his Welsh roots and because she tolerated his wildness.

During the 1950s Burton had numerous affairs with other women, including the actresses Claire Bloom, Jean Simmons and Susan Strasberg. Burton’s biographer, Melvyn Bragg, wrote that “the flow of ladies to and from the Burton dressing room — so gossip had it — was like river traffic around New Orleans at Mardi Gras”.

In 1962, however, things became more serious after Burton began a very public affair with Elizabeth Taylor, his co-star in Cleopatra. A friend of the couple described them as “a pair of sexual comets unleashed… hurled along with their own boldness”. Elizabeth Taylor was denounced by the Vatican, and a US congresswoman sought to have the adulterous pair barred from entering the country.

Although he could not overcome his infatuation, Burton dithered for some time about breaking up his marriage to Sybil. His family adored her, and his beloved elder brother Ivor disapproved so violently that he refused to speak to Richard. One evening, Elizabeth Taylor sent Burton to Sybil to ask for a divorce; but when he arrived and Sybil asked him: “Have you come to stay?” Burton replied: “Yes.” It was not until five weeks into their next film together, The VIPs (1963), that Burton finally asked Elizabeth Taylor to marry him. Divorce proceedings followed, Sybil winning custody of their daughters and a settlement of $1 million — a huge sum at the time. Eventually Burton’s old theatre friends and his Welsh family forgave him, while public opinion, initially very much on Sybil’s side, soon yielded to the romance of the fiery Burton-Taylor relationship.

Sybil Williams was born at Tylorstown, a village in the Rhondda Valley, on March 27 1929. Her father was a coal miner who rose to be a colliery undermanager. Her mother, a seamstress, died when Sybil was 10, and when her father died five years later she went to live with an elder sister and her husband in Northampton.

There, after working for a time as a window dresser, she gained a place at the London Academy of Dramatic Arts. It was during her last year there that she was offered a job as an extra in The Last Days of Dolwyn.

In the early years of her marriage Sybil Burton played Lady Mortimer in Henry IV at Stratford, and appeared in Harvey in the West End, and (with her husband) in the radio production of Dylan Thomas’s Under Milk Wood. But her heart was not in it, and she soon gave up acting to support her husband.

After their separation, Sybil took her children and fled to New York, where she threw herself into a new life in an apartment overlooking Central Park.

In the early 1960s she became involved in the New Theater on East 54th Street, where she opened a discotheque, Arthur’s. The venture was so successful that she opened a branch in Los Angeles called The Other Place. In 1991 she co-founded the Bay Street Theatre, a non-profit theatre on Long Island. She served as its artistic director until last year.

In 1964 she married Jordan Christopher, an American pop star 14 years her junior. She had a third daughter with him, and they enjoyed a happy family life together until Christopher’s death in 1996.

Sybil and Jordan – above – They look very happy together !!!

Sybil Christopher took a philosophical view of the breakdown of her first marriage, describing it as “just something that happened”.

She is survived by her three daughters.