William Basset married Cecilia, heiress of the de Dunstanville family, in the mid-twelfth century, and the manor of Tehidy passed into Basset hands as her dowry. The name is recorded as 'Tehidin' in the twelfth and thirteenth centuries, derived from the Cornish 'ti', meaning a house, attached to a personal name nobody quite remembers. By 1330 the Bassets owned a substantial building here. In 1497, during the first Cornish Rebellion, rebels led by Richard Pendyne of Pendeen took out their fury on the house in revenge for the loyalty its owner, John Basset — then Sheriff of Cornwall — had shown to Henry VII. They pulled it apart stone by stone. The family rebuilt. They had the money: Tehidy sat on the edge of Cornwall's richest tin-mining country, and the Bassets owned shares in Dolcoath, Wheal Basset, and a string of other mines. In 1860 and 1861 alone, John Francis Basset took £20,000 in mining income, enough to commission a complete rebuilding of the house. The new mansion was finished in 1863.

By 1888 the tin price was sinking and the mining income with it. Arthur Francis Basset inherited an estate he could no longer easily fund, and by 1915 the mansion was vacant. The next year, after seven centuries on the land, the family sold up. In 1918 the abandoned house was converted into an isolation hospital for tuberculosis patients — the disease was carving through industrial Cornwall with particular savagery, and remote country estates with their fresh-air wards were the standard treatment. On 23 February 1919 the building burned to the ground. By January 1922 it had been completely rebuilt. The Tehidy Hospital, sometimes called Tehidy Sanatorium, kept running for sixty more years. In later decades it took stroke, head injury, and respiratory patients alongside TB cases. The operating theatre was refurbished in the early 1980s and then, oddly, never reopened. The hospital shut for good in April 1988. The buildings have since become luxury apartments and the central section is private property with no public right of way.

What Cornwall Council bought in 1983, and what 250,000 visitors a year come for now, was always the parkland rather than the house. The Bassets had laid out the woodland in the great-park English tradition: ash, alder, oak, beech, sycamore, birch and chestnut at the canopy, with hazel and holly beneath, rhododendron in dense banks where the Victorians wanted colour, and Allium triquetrum — wild garlic — carpeting the floor in late spring with white bells and the unmistakable scent. Bluebells flower in great drifts in April and May. Daffodils naturalised across the lawns. The lake at the bottom of the slope holds swans and geese; the deeper pools attract otters. Grey squirrels and badgers work the leaf litter. Rooks and jackdaws nest in the high beeches. The woods are big enough to be quietly disorientating: 250 acres of mixed canopy is enough cover to lose a Sunday in.

Tehidy is one of four country parks in Cornwall, and the only one with this density of canopy cover. The park's facilities are unfussy: a permanent orienteering course laid out through the woodland, an events field for fetes and outdoor concerts, a campsite for schools and youth groups, and a designated area where you can hire barbecue pits among the trees. Mountain bikers use the surfaced paths. Horse riders use the bridleways. The South West Coast Path, which threads its way around the entire Cornish peninsula, passes within walking distance to the north, so Tehidy has become a popular inland diversion for coastal hikers who want a half-day in shaded woodland between sea-cliff stages. There is no formal entry charge. The car parks fill on summer weekends and empty by dusk.

From the air Tehidy is unmistakable in mining country: a single dark green block of mature woodland in the otherwise open landscape of fields and former workings between Camborne and the north coast. The lake at the southern edge catches afternoon light. The rebuilt Tehidy House sits in the centre of the canopy, its luxury flats invisible from above under the beech crowns.