Complex sentence: By this point, her marriage to the womanizing John Osborne was already in turmoil and in 1959 she began an affair with actor Robert Shaw while they co-starred in "The Changeling" at London's Royal Court Theatre.
Split into simpler sentences: By this point, her marriage to the womanizing John Osborne was in turmoil. In 1959 she began an affair with actor Robert Shaw, her co-star in "The Changeling" at London's Royal Court Theatre.