Complex sentence: Until the 12th century, much of Pembrokeshire would have been virgin woodland, and clearance in the lowland south began under Anglo-Flemish colonisation and under mediaeval tenancies in other areas.
Split into simpler sentences: Until the 12th century, much of Pembrokeshire was virgin woodland. Clearance in the lowland south began under Anglo-Flemish colonisation and under mediaeval tenancies in other areas.