The Cornish rotten and pocket boroughs were one of the most striking anomalies of the Unreformed House of Commons in the Parliament of the United Kingdom before the Reform Act 1832.
Most of these were rotten boroughs, a term meaning communities which had decreased in size and importance since the Middle Ages and were too small to justify separate representation.
Of the six boroughs continuously represented in the House of Commons of England since medieval times, five (Bodmin, Helston, Launceston, Liskeard and Truro) could be considered the county's chief towns and survived the Reform Act, while the sixth (Lostwithiel) was probably once substantial enough even though it had dwindled by 1832.
The explanation can probably be found in the way that most new boroughs arose at this period, as a result of a petition from the town in question receiving support from some figure with sufficient influence at court to secure its acceptance.
The extent of Royal influence in Cornwall may therefore only have been a factor in the sense that it explains why it was the natural place for a disproportionate number of influential courtiers to set up proprietary boroughs.
In some, all or most of the (male) householders could vote, the electorates in some cases being as high as a few hundred: in these, control might depend on appealing to the voters' venial interests, usually through bribery (open or otherwise) but also through the potential for coercion; where a poor voter was aware how his landlord wanted him to vote, it is unrealistic to attempt to distinguish between the two, and properties were of course frequently bought and sold purely for their electoral value.
The Reform Act 1832 disenfranchised all but seven of the Cornish boroughs, and one of those (Penryn) while technically surviving had been entirely swamped by the addition of a larger neighbouring town.