« Reply #5 on: Saturday 16 September 23 10:01 BST (UK) »
There were probably many cases like this, most of them unlikely to be easy to find on the net. The one that I remember (also from the 1970s) concerned Ashton-under-Lyne, in Greater Manchester, a very different place. I can't find confirmation of that. More generally, I have read that the invention of the bicycle made the largest single contribution to the decrease in in-breeding in rural England.
Cornish (Devon), Bowden (Cornwall, Devon), Kitson (Devon, not North Lancashire), Karslake (Devon), Eales (Devon), Churchill (Dorset -- no known connection with Sir Winston), Duncan (Ireland), Colclough (Ireland, not Staffordshire), McMurtry (Ireland), Browning (Hampshire, Dumfries), Heberden (various), Rogers (Thurlestone, Devon)