Complex sentence: The Captain of the "Empress" in 1941-42 would only realize many years later that he'd had a VIP aboard--a young Midshipman Philip Mountbatten (later to become Duke of Edinburgh) is remembered for having helped stoke the boilers in 1941.
Split into simpler sentences: The Captain of the "Empress" in 1941-42 would only learn years later that he'd had a VIP aboard. A young Midshipman Philip Mountbatten (later to become Duke of Edinburgh) helped stoke the boilers in 1941.