Thumbing through the dictionary after looking up a word I find an entry for the “Lansker line.” This is defined as “the linguistic and ethnic division between the Welsh-speaking north and the English-speaking south” of Pembrokeshire. The etymology is 19th century Pembrokeshire dialect.
Wikipedia has an entry on it where it is spelled “landsker.” Here’s the map with the boundary.
The entry states:
The English-speaking areas, known as Little England beyond Wales, are notable for having been English linguistically and culturally for many centuries despite being far from the border with England. The line is noted for being sharp, and for having moved only slightly over the past several centuries.
I was not previously familiar with this fascinating piece of political geography and boundary-making. I think it’s pretty unusual for a line to be sharp, and remain so, after so long a period of time. It makes you wonder what other boundaries are similarly well-defined. Today, we more often speak of cross- or trans-border relations, and that boundaries are artificial and, at best, fuzzy. This is a good counter-example.