Ms. York, who was born in London in 1939 to a distinguished family of politicians and business magnates, emerged as a sensuous, blonde, blue-eyed star of cinema in the 1960s. Her career began in 1960's "Tunes of Glory," in which she played opposite Alec Guinness, but she burst forth in Tony Richardson's rollicking, lusty adaptation of Henry Fielding's "Tom Jones," playing Sophie Western, the libidinous hero's true love.

She followed this role with parts in "A Man for All Seasons" and "The Killing of Sister George," where she appeared in a nude lesbian scene, before being cast in the Depression-era-set "Horses" alongside Gig Young and Jane Fonda. She made news when she expressed herself offended at having been nominated for an Academy Award without being asked. Nevertheless, she didn't win the award. She did, however, take the BAFTA prize for the same performance.

In 1972, she won the Best Actress award at Cannes for Robert Altman's "Images." Still, moviegoers may know her best for her part as Superman's mother Lara in the 1978 hit, as well as its sequels "Superman II" and "Superman IV."

Ms. York consistently made time for stage roles. She appeared in 1978 at the New Theatre in London in The Singular Life of Albert Nobbs. Her most recent UK stage appearances were with the RSC in The Merry Wives of Windsor, Hamlet and Camino Real in Stratford and London; independent productions of An Ideal Husband and Small Craft Warnings in London; and a national tour of David Hare's Amy's View.

In 2007, she toured the UK in Wings of the Dove. She also toured internationally in a solo show called The Loves of Shakespeare's Women, which was inspired by John Gielgud's stage show, The Ages of Man. Her final stage performance was in Ronald Harwood's Quartet at the Oxford Playhouse in summer 2010. "I'm an infinitely better actress now than I was 30 years ago because I've had experiences and I've learned," she said in 2005. "I do look back on some roles and think I was dreadful, but I'm not going to tell you which performances I'm talking about."

Susannah Yolande Fletcher was the daughter of Simon William Peel Vickers Fletcher, a banker and steel titan, and his first wife, the former Joan Nita Mary Bowring. Her maternal grandfather was Walter Andrew Bowring, a British diplomat, and her great-great-grandfather was political economist Sir John Bowring. In early 1943, her mother married a Scottish businessman, Adam M. Hamilton, and moved, with her daughter, to Scotland. She began her acting training at RADA, where she won the Ronson award for most promising student and graduated in 1958.

In 1960, Ms. York married Michael Wells and later had two children.