Complex sentence: The Cornovii were a people of Iron Age and Roman Britain, who lived principally in the modern counties of North Staffordshire, Shropshire and Cheshire in the English West Midlands; moreover, Ptolemy references presence of the "Cornivii" as far south as Gloucestershire.
Split into simpler sentences: The Cornovii were a people of Iron Age and Roman Britain, who lived principally in the modern counties of North Staffordshire, Shropshire and Cheshire in the English West Midlands. Ptolemy also references presence of the "Cornivii" as far south as Gloucestershire.