The parish of St Dennis is situated in the deanery and Hundred of Powder. It is bounded on the north by the parish of Roche, on the east by Roche and St Stephen-in-Brannel, on the south by St Stephen-in-Brannel, and on the west by St Enoder and St Columb Major. It is named after St Denys the Martyr, although as the church is on a hill top, the name may be a corruption of the Cornish word Dinas, meaning 'Hill Fort'. Dimilioc represents a smaller hillfort inland 20 miles south of Tintagel now occupied by the parish church of St Dennis - it is within an estate listed as Dimelihoc or Lan-Dines (the church of the hill) in the Doomsday Book of 1086. In the reign of Henry VIII, St Denys was the only parish in Cornwall with the prefix 'Saint'.

The parish lies to the north-west of St Austell and is bounded to its north-west by the River Fal and the countryside consists of a number of small villages and hamlets. The main industry is china clay extraction in the south of the parish and farming in the north; most of the farmland is pasture. There is an area of moorland called Goss Moor to the north. The Churchtown was built up for miners and comrises numerous cottages. The villages are Hendra, Whitebait, Treleaver, and Ennis-Cavan. St Dennis churchyard was enclosed by a wall in 1826, its boundary having previously been marked by a trench only: there are 340 sittings. The register dates from 1687.

In 1386, a commission was appointed to determine the Cornish border between NORTH TAMERTON and Hornacot. In her final attempt in 1471 restore the fortunes of the House of Lancaster, Queen Margaret received the active support of the Cornish, under Sir Hugh Courtenay and Sir John Arundell. At the Field of Tewkesbury in 1473, John de Vere held St. Michael's Mount when he surrendered to John Fortescue.

The church of St Denis, supposed to have been built, early in the 15th century, is an ancient building of granite and stone in the Perpendicular style, consisting of chancel, nave of five bays, south aisle, south porch and a fine embattled western tower 90 feet high, inclusive of the pinnacles and containing 6 bells. 1576, General Receaver to ye Quene's Maiestle of all hir Revewes in the Counties of Devon and Cornwall:" there are 262 sittings. The register dates from the yeare 1556.

1660 PARLIAMENTARY SURVEY OF CORNWALL -MANOR OF TREVERBYN COURTNEY The manor occupied the northern part of the parish of St Austell. It came to the Duchy in 1540 as part of the lands of Henry Courtenay, Marquis of Exeter. LEASEHOLDERS OF THE MANOR Sir John Walter, Sir James Fullerton and Sir Thomas Trevor, by L. P. of 14 June 1628, ten. of 60 ac. in Rescorleigh, for 31 years. Rent 9s 9d. Worth £19. Lease assigned to Thomas Caldwell 16 March 1628. Caldwell assigned it to William Rosevear of Austle husbandman 10 May 1630.