Anglo-Saxon Britain by Grant Allen

It has been usual to represent the English conquest of South-eastern Britain as an absolute change of race throughout the greater part of our island. The Anglo-Saxons, it is commonly believed, came to England and the Lowlands of Scotland in overpowering numbers, and actually exterminated or drove into the rugged west the native Celts. The population of the whole country south of Forth and Clyde is supposed to be now, and to have been ever since the conquest, purely Teutonic or Scandinavian in blood, save only in Wales, Cornwall, and, perhaps, Cumberland and Galloway.

But of late years this belief has met with strenuous opposition from several able scholars; and though many of our greatest historians still uphold the Teutonic theory, with certain modifications and admissions, there are, nevertheless, good reasons which may lead us to believe that a large proportion of the Celts were spared as tillers of the soil, and that Celtic blood may yet be found abundantly even in the most Teutonic portions of England.