Complex sentence: At this time, Devon was controlled by a group of large landowners principally in the Courtenay, Bampfylde and Rolle families who had so many supporters that no other challenge was possible; due to the expense, the county had not seen a contested election since 1712.
Split into simpler sentences: At this time, Devon was controlled by a group of large landowners principally in the Courtenay, Bampfylde and Rolle families who had so many supporters that no other challenge was possible. Due to the prohibitive expense of mounting an opposition, the county had not seen a contested election since 1712.