Complex sentence: Shortly after, at 9:56, Somerville received the report of his own aircraft from the carrier HMS "Ark Royal" about the presence of five cruisers and five destroyers, and assumed that these were Italian units closing for battle.
Split into simpler sentences: Shortly after, at 9:56, Somerville received the report of his own aircraft from the carrier HMS "Ark Royal" about the presence of five cruisers and five destroyers. The British Admiral assumed that these were Italian units closing for battle.