The constituency was a parliamentary borough in Somerset, first represented in the English Parliament in 1298 but thereafter returning MPs only occasionally until its right to representation was revived by a resolution of the House of Commons in 1621.
Ilchester was a "potwalloper" borough, meaning that the right to vote was exercised by all inhabitant householders not receiving alms (a household being theoretically defined by having a separate hearth on which a pot could be boiled); in the 18th century this amounted to a couple of hundred voters, who expected to receive full value in return for their votes, either at the time of election or later.
The Whig interests in the borough at this time were managed by one of the MPs, Thomas Lockyer, nicknamed "Snowball" for the way in which he accumulated money, and the government spent £1000 on securing the election of John Talbot as the other member.
At around the same period Lord Chesterfield records in his Letters to His Son that he investigated buying him a seat in Parliament at Ilchester and was quoted a price of £1500.
After this reverse, however, he took more drastic action to secure his influence, having most of the houses in the town pulled down (their former occupiers thereby losing their votes), reducing the electorate to about 60.