The Domesday Book of 1086 records the manor as Bochenod, one of many holdings of Robert, Count of Mortain, half-brother to William the Conqueror. The tenant who actually worked the place was a Briton known by half a dozen spellings of his name. Twelve manors he held in Devon and Cornwall after the Conquest, where twenty had been his before. The land passed in succession through the Carminow family, then the Courtenays of Devon, then back to the crown by attainder, then to the Russells, Earls of Bedford. Sir William Mohun bought it in 1579, claiming descent from one of the Courtenay co-heiresses. The Mohuns kept it for a century and a quarter, until the widow of the 4th Baron Mohun sold the estate to Thomas Pitt around 1717. The diamond had done its work.

Thomas Pitt was the grandfather of William Pitt the Elder, who would lead Britain through the Seven Years' War, and the great-grandfather of William Pitt the Younger, who would lead it through the French Revolution. Two prime ministers in three generations. Pitt the elder bought rotten boroughs alongside the estate: Old Sarum in Wiltshire, where he nominated both MPs, Okehampton in Devon, where he nominated one, plus considerable sway at Camelford and Grampound in Cornwall. Family members filled those seats and built influence at Westminster on Cornish soil. Thomas Pitt of Boconnoc, son of the diamond merchant, became Lord Warden of the Stannaries. His son Thomas Pitt, 1st Baron Camelford, developed china clay mining on the estate and added a south wing to the house in 1772 as a picture gallery. He died in Italy, but his body was carried home and buried in the small parish church behind the house. The south wing he built was demolished in 1971.

The estate passed in 1864 to George Matthew Fortescue, second son of the Earl Fortescue, through his aunt Anne Pitt. Fortescues held Boconnoc for the next century and a half. They served as High Sheriffs of Cornwall, fought in the Coldstream Guards, married into other Cornish families. Captain Desmond Grenville Fortescue, who died in 2017 at ninety-eight, handed management to his son Anthony in his old age. On 9 November 2015, Anthony Fortescue was found dead inside Boconnoc House following a firearms incident. The inquest returned an open verdict. He left two daughters as co-heiresses, and predeceased his father by two years. The Boconnoc Cricket Club still plays in the deer park. In 1993 the estate stood in for seventeenth-century France in the film of The Three Musketeers.

Parts of the ancient deer park around Boconnoc House shelter old-growth sessile oaks growing in steep ravines and on south-facing slopes. The lichens that drape them form what botanists call an internationally important assemblage, one of the most significant sites in Europe. Plantlife designated the area an Important Plant Area; Natural England named it a Site of Special Scientific Interest in 1986. Lichens are slow growers and intolerant of pollution; their richness here is testament to centuries of stable, undisturbed canopy. The site is considered the finest example of southern-oceanic old-growth oak woodland in the southwest of England. Pilots flying over see only rolling green and the silver thread of the River Lerryn winding through it. The biological wealth is hidden beneath the canopy, where the lichens have done what the Pitts and Fortescues did: stayed put, and gathered.

A Methodist chapel stood at Trecangate from 1820 to 1954, built of cob, its position marked now only by a sign erected in 2009. Cornish wrestling tournaments drew crowds here in the 1700s. The parish church behind the house has no known dedication, an oddity in itself; inside, a fifteenth-century font, a Jacobean pulpit, an altar table made by Sir Reginald Mohun in 1621, and a monument to Penelope Mohun who died in 1637. The tower has five sides in its lower stage and eight in its upper. The hamlets of Couch's Mill and Brooks complete the parish. Ninety-six people, by the 2011 count. The Domesday tenant Osfrith would have known fewer.