Complex sentence: Maureen's involvement with Ballet when she returned to England from 1978 onwards was mainly as an examiner for the Royal School of Ballet, and two years before she died she was made the Chief Examiner of that organisation.
Split into simpler sentences: Maureen's involvement with Ballet when she returned to England from 1978 onwards was mainly as an examiner for the Royal School of Ballet. Two years before she died she was made the Chief Examiner of that organisation.