Note incidentally the English-sounding name, Anglesey. The Welsh name is given as Ynys Môn, though I have not investigated the starting-points of these names.
Anglesey is mentioned in Julius Caesar—one of his economic reasons for invading England was wheat, from Anglesey; plus tin, lead, cattle. And note the geographical position: Anglesey has a mild climate (the Gulf Stream helps), and has naturally sheltered harbours.
His paper on J K Rowling suggests the same thing: millions of people in London have been to King's Cross and Euston, seen the new British Library and London University buildings, and felt familiar with cafés and offices and shops and traffic.
But these are just the façades—built equivalents of political puppets and their movements and sideshows—the real work is done secretly behind closed doors.
Hilaire Belloc wrote on the likely landing-place(s) of Caesar, based on his personal knowledge of sailing, and this sort of thing is needed to assess Anglesey.