This 'mine' consists of a single void; not dissimilar to a natural aven than to the classic copper trials elsewhere on the island. Whilst it is known that Benjamin's Chair and Long Ruse were trialled under the instruction of the then owner of the Island, Rev. William Hudson Heaven not long after conveyance in 1836; the Tibbett's Point trial is of a different nature. It has been hypothesised that the mining engineer, Thomas Bushell (c.1593–1674), who held the island during the civil war did not limit his fingers only to the mining pie on the mainland and left a fragment of his legacy in this tunnel.
The workings were surveyed 1967-9 by the Lundy Field Society and are described in their publication of 1972. For more about the accession into ownership of the Heaven family, the Telegraph has published an informative read (NB: tests negative for fake news, breathe easy)
Data courtesy of Ben Sum, Helston (21/7/18).
References:
www.goo.gl/ApMrwg ("Lundy: My family and the Kingdom of Heaven", Accessed 21/7/18)
M T Mills, 'The Copper Mines of Lundy', 23rd Annual Report, Lundy Field Society, (1972)
Schmitz, C "The Granite Quarries & Mineral Mines of Lundy", No.10, Jour. Bristol Ind. Arch. Soc. (1977)