Cornelly parish was united with Cuby in 1934. The population of Cuby with Tregony parish at the 2011 census was 1015. Tregony was at the head of a navigable channel in medieval times but the River Fal became badly silted due to tin streaming and its sea-borne trade went to Truro.
The church of Cuby is dedicated to Saint Cuby, a Welsh saint: since the parish church of Tregony was lost to the River Fal ca. 1540 Cuby Parish Church has been in fact the parish church of Tregony also. The church was rebuilt in 1828 though some of the medieval masonry still exists on the north side and the tower (of two stages) is of the 14th century. In the south aisle is an inscribed stone of the 6th or 7th century (Nonnita Ercilini Rigati [...]tris Fili Ercilini). The church in Norman times belonged to the alien priory at Tregony but in 1278 ownership passed to Merton Priory in Surrey,