In the middle of the nineteenth century, Cornish tin and copper mines were being driven out under the beach and beyond the low-water mark. Nobody could say with confidence who owned what lay underneath. The Crown presumptively owns the soil between high and low water around the English coast, but in Cornwall a string of grants going back to the charters of Edward III had given the Duke of Cornwall, the sovereign’s eldest son, extensive rights over the county. Accumulated mineral income was sitting unclaimed, and the uncertainty had stalled new workings along the shore.
Rather than litigate, the two sides agreed in 1856 to put the question to arbitration. Lord Cranworth acted for the Crown and Thomas Pemberton Leigh, later Lord Kingsdown, for the Duchy. The arbitrator was Sir John Patteson, a retired judge of the Queen’s Bench. According to the Solicitor-General’s account to the House of Commons, Patteson worked through the documents from February 1856 to June 1857 and then issued his award; a further point was settled in February 1858.
What was argued
The Duchy’s case was ambitious. Its lawyers contended that Cornwall had been a distinct territory before the Norman Conquest, that the medieval Earls of Cornwall had held the county with the rights of a county palatine, and that those rights had passed, enlarged, to the Duchy when it was created in 1337. They pointed to past exercises of what look like sovereign powers, such as seizing enemy ships and collecting customs, and described the duke as “quasi sovereign” within the Duchy, standing in the place of the king. The Crown answered that the earldom had escheated to the Crown in 1336, that the Duchy held only what its charters expressly granted, and that the foreshore, being a sovereign right, would have needed an express grant it never received.
Patteson split the difference by geography. The strip between high and low water, and the minerals beneath it, went to the Duchy. The bed of the sea below low-water mark, together with the beds of estuaries and tidal rivers, stayed with the Crown. Because the Crown could not reach its submarine minerals without crossing Duchy ground, Patteson proposed a working arrangement, and that is what the Cornwall Submarine Mines Act 1858 enacted. The Act received royal assent on August 2, 1858. It vests the minerals below low-water mark in the Crown “as part of the soil and territorial possessions of the Crown” and provides for compensation where Duchy land between the tide lines is used to get at them.
The investigation
The Act did not pass without objection. In committee on July 19, 1858, the MP Augustus Smith argued that the Bill’s real reach went beyond its title and could affect public rights over the foreshore, and he moved to delay it until the arbitration papers were laid before the House. The Solicitor-General replied that the measure bound only the Crown and the Duchy, with a saving clause for everyone else, and the amendment was rejected. Modern legal historians have noted how thin the formal record is: Henry Jones, writing in the British Yearbook of International Law in 2026, points out that the award itself runs to less than a page and offers no legal reasoning. Jones argues that the conceptual work done in this obscure dispute, extending territory and sovereignty out under the sea, later fed into the international law of the continental shelf.
The explanations
For Cornish nationalists the case has become a touchstone. The Duchy’s own counsel said in writing that the duke was quasi sovereign and that the Crown had surrendered its territorial dominion in Cornwall, and the Duchy won. Some writers have gone further and alleged that between 1858 and the Local Government Act 1888 officials quietly erased the consequences of the award, altering charters and losing statutes to fold Cornwall back into England. No archival evidence for such a scheme has been published, and the claim rests on inference from the fact that later legislation treated Cornwall as an ordinary county.
A more measured critique comes from the notary and legal scholar John Kirkhope, who observes that the Duchy claimed near-royal status in the 1850s when that claim was financially useful and now describes itself as a private estate. His question is when, if ever, the Duchy stopped being quasi sovereign. That is a fair point about consistency, but it is not the same as showing that the 1858 award recognized Cornish nationhood. Arbitration awards settle the dispute in front of the arbitrator. This one settled mineral rights.
Where it stands
The Cornwall Submarine Mines Act remains on the statute book, partly repealed, and the Duchy still owns most of the Cornish foreshore. The constitutional significance of the case is a matter of interpretation rather than fact. What the record supports is narrower and stranger than either side’s summary: a Victorian property dispute, argued with medieval charters, in which the heir to the throne’s officers told a judge that their master was practically a king in Cornwall, and the judge gave them the beach.