Both were largely of mixed Danish and Anglo-Saxon blood; for, when William the Conqueror carried fire and sword through Northumbria, great numbers of the inhabitants moved north, and settled in the district beyond the reach of the Norman arms.
On the English side of the border the population were, in time, leavened by Norman blood; as the estates were granted by William to his barons.

These often married the heiresses of the dispossessed families, while their followers found wives among the native population.
The frequent wars with the Scots, in which every man capable of bearing arms in the Northern Counties had to take part; and the incessant border warfare, maintained a most martial spirit among the population, who considered retaliation for injuries received to be a natural and lawful act.

This was, to some extent, heightened by the fact that the terms of many of the truces specifically permitted those who had suffered losses on either side to pursue their plunderers across the border.

These raids were not accompanied by bloodshed, except when resistance was made; for between the people, descended as they were from a common stock, there was no active animosity, and at ordinary times there was free and friendly intercourse between them.
There were, however, many exceptions to the rule that unresisting persons were not injured.

Between many families on opposite sides of the border there existed blood feuds, arising from the fact that members of one or the other had been killed in forays; and in these cases bitter and bloody reprisals were made, on either side.