John Knill was an articled clerk to a solicitor in Penzance and was a Collector of Customs at St. Ives between 1762 and 1782. He was also Mayor of the town in 1767.
He was a well-respected citizen and travelled a lot in a time when roads were little more that cart tracks, and where all communication was poor. In his position as Customs Officer, both in St. Ives and London, his advice was eagerly sought and he inspected Custom Houses as far away as Jamaica. He also became a magistrate; was called to The Bar and was Treasurer to the Bench of the Inn. He appeared to enjoy life to the full and socially he met many eminent people, including John Wesley and the engineer John Smeaton. In 1782 he had a three-sided stone obelisk built high on a hill as a landmark to those at sea.