Complex sentence: He served as Defence Secretary for the United Kingdom from 1997 to 1999, before taking up his NATO position and becoming a life peer as Baron Robertson of Port Ellen, of Islay in Argyll and Bute.
Split into simpler sentences: He served as Defence Secretary for the United Kingdom from 1997 to 1999, before taking up his NATO position. After his retirement he was made a life peer as Baron Robertson of Port Ellen, of Islay in Argyll and Bute.