Complex sentence: However, he also excelled as a student and seriously considered becoming a doctor and had an offer to go to university after his National Service at age 18, which, in the event, he turned down.
Split into simpler sentences: However, he also excelled as a student, and seriously considered becoming a doctor. He had the offer of a university place on completion of his period of compulsorymilitary service which, in the event, he turned down.