London Review of Books 45 (2023), 6

Rosemary Hill discusses John Smeaton’s ingenious design for the reconstructed Eddystone lighthouse (LRB, 16 February). She doesn’t mention that in order to anchor the lighthouse securely at the base, Smeaton sliced off a fair chunk from the top of the House Rock on which it stands. This gave rise to a curious incident two centuries later, when, in the course of the UK/French arbitration on the delimitation of the continental shelf in the 1970s, France claimed that the result had been to convert what had previously been an island into a ‘low tide elevation’, which would be covered by the sea at high tide. In consequence, the argument ran, the rock was no longer entitled to serve as a base point for the deciding of maritime limits. The drawings in Smeaton’s Narrative of 1791 suggest that he might have taken off as much as 4.3 feet. There would, of course, have been no way to check that two hundred years later other than by dismantling the lighthouse to reveal the rock beneath, then recording the levels of contemporary tidal movements, which vary considerably in that part of the English Channel. The Court of Arbitration, happy to say, found an elegant way to sidestep the question, and Eddystone does still serve as a base point for the measurement of the median line between the UK and France.