Complex sentence: Duncan was educated at Cheltenham College (hence their reason for having the Cross from 1978 until 1998) and joined the Royal Navy, after being prepared at North Grove House Academy, and was assigned to HMS Euryalus on the East Indies station.
Split into simpler sentences: Duncan was educated at Cheltenham College (hence their reason for having the Cross from 1978 until 1998) and joined the Royal Navy. He was assigned to HMS Euryalus on the East Indies station.