[3] In July 2023 the hill was listed by Estate Agents for £150,000 and bought by the Cornwall Heritage Trust in November.

On the deeper soils European gorse (Ulex europaeus), bracken (Pteridium aquilinum) and bramble (Rubus fruticosus) are the dominant scrub species.

[6] The nationally scarce moss (Brachydontium trichodes) known from only two sites in Cornwall also occurs on Tregonning Hill.

[9] Due to scrub and tree growth it is in a poor condition and is on Historic England's, Heritage at Risk Register.

[3] While visiting the area in 1745, William Cookworthy, a Plymouth chemist observed a very fine clay being used to repair furnaces.

The tankard, now in the collection of the British Museum, features a scrolling banner with the name of Cookworthy's fledgling pottery, "Plymouth Manufactory" around the arms of the city of Plymouth, painted in underglaze blue, and a date and maker's mark on the base, "March 14, 1768 C.[ookworthy] F.[ecit][2] In the 1870s china clay from Tregonning, and a 30 to 40 acre quarry at Tresowes on the western side of hill, was shipped from Porthleven; the amounts were 92 tons in 1876, 130 in 1877, 61 in 1878, 136 in 1879 and none in 1880.

[17] In the early 1870s the Tregonning Hill China Clay and Brick Works was established by William Argall.

[21] In 1880 The Cornishman reported on the annual custom, by the Ashtown Free Church Sunday scholars (Ashton), to walk in procession to the ″old amphitheatre″ for a sermon.