An unusual survival in the annals of recorded mining history, Wheal an Cowes ("the Work of the Excavation") owes its recognition to a 16yr lawsuit in 1387 whereby an number of local tinners brought legal action against the Duchy of Cornwall for perceived unlawful eviction from their work somewhere in the Lamorna Valley, St Buryan. The men were John Treweof, John Urban and Roger Trewethenek; the case, which is recorded through the Chancery's close and patent rolls, reads:
"July 29. 
Appointment of John Treweof, John Urban and Roger Trewethenek, Westminster, to enquire for what cause a certain tin work called 'Coweswerk' in Lamorna, Cornwall, was lately seized into the king's hands, as forfeited, by John Bery, escheator in that county, and whether, by the procurance of certain persons scheming to defraud the king thereof, lie concealed the true cause of the seizure and returned a sinister inquisition touching the same into Chancery."
It is later revealed that "John Bery" - in whose name the bounds were registered (the registration has not survived) - had been killed by a fall of ground in the work, suggesting that while quoted as a stream work it was likely an early example of lode mining.
What this case also reveals is the earliest example of tin bounding considered a form of "chattels real"; Bery owned the bounds such that upon death they could be seized by the Duchy vis escheat from the crown.
Tinners prior to the Tudor upheaval to the systems of mining were something of a villein class during the medieval period, much more free than common feofs or vassals. Tinworks during this period were pitched in wastral, unenclosed ground without consent of the landowner, merely requiring rents and dues to be paid retrospectively. Bounds required registration however so as to limit the issue of disputes.
Simply because the Duchy owned the land did not mean they owned unimpeded access to the mine. What this case displays is that tinners had a right to their works - in sympathy with the 1201 charter - which granted them possession of that area of land, but not ownership.
Data courtesy of Ben Sum, Helston (25/6/18)
Public Records Office, 1900,"Calendar of the Patent Rolls, RICHARD II A.D. 1386—1389", Norfolk
Buckley, A, 2009 "The Tudor Tin Industry", Penhellick