Complex sentence: Sir John Blelloch KBE was Permanent Under Secretary of State at the Northern Ireland Office from 1988 to 1990, having previously served as a Deputy Secretary in that Office from 1980 to 1982, while resident in Northern Ireland.
Split into simpler sentences: Sir John Blelloch KBE was Permanent Under Secretary of State at the Northern Ireland Office from 1988 to 1990. He served as a Deputy Secretary in the Northern Ireland Office Office from 1980 to 1982, while resident in Northern Ireland.