Complex sentence: The British were unaware that Italian reconnaissance aircraft had spotted the sailings from both ends of the Mediterranean and set up submarine ambushes, and that two Italian battleships, three cruisers and two destroyer flotillas had left harbour, more cruisers, destroyers and torpedo boats following.
Split into simpler sentences: The British were unaware that Italian reconnaissance aircraft had spotted the sailings from both ends of the Mediterranean and set up submarine ambushes. Two Italian battleships, three cruisers and two destroyer flotillas had left harbour, more cruisers, destroyers and torpedo boats following.