Complex sentence: In 1964 he joined Aberdeen University as senior lecturer progressing to Professor of English from 1965--68 and then became Regius Professor of English Literature from 1968-84 also holding various other administrative positions.
Split into simpler sentences: In 1964 he joined Aberdeen University as senior lecturer progressing to Professor of English from 1965 to 1968. He then became Regius Professor of English Literature from 1968 to 1984, also holding various other administrative positions.