Complex sentence: The chief place was seemingly the former Roman Viroconium Cornoviorum (modern Wroxeter), the former civitas of the Cornovii, and the kingdom may have covered much of modern Cheshire, Shropshire and into North East Wales, Wrexham, Denbighshire and Flintshire.
Split into simpler sentences: The chief place was seemingly the former Roman Viroconium Cornoviorum (modern Wroxeter), the former civitas of the Cornovii. The kingdom may have covered much of modern Cheshire, Shropshire and into North East Wales, Wrexham, Denbighshire and Flintshire.