Complex sentence: King gained a B.A. in History and Economics at Queen's University, Ontario, before he came to the UK as a Rhodes Scholar to study Philosophy, Politics and Economics at the University of Oxford, after which he gained a D.Phil.
Split into simpler sentences: King gained a B.A. in History and Economics at Queen's University, Ontario. He then moved to the UK as a Rhodes Scholar to study Philosophy, Politics and Economics at the University of Oxford, after which he gained a D.Phil.