I think one should include the Wars of Scottish Independence when considering relations between the Scots and the English. I lived in Edinburgh and Glasgow consecutively for ten years, and eventually it dawned on me just how much the English were detested 'up there'.
As I said, my name was very Scottish, and I took on the accent of both cities, which helped my integration.

My bibulous Scottish boyfriend took me to many rugby matches between Scotland and England. I was under strict instructions not to shout for the latter or I'd be flattened.

When 'O Flow'r of Scotland' was bellowed out by the Scottish supporters, the animosity and hatred were palpable.

He once took me to his parent's house in Fife for 'tea'. His family were aghast that he'd actually got an English girlfriend, and positively bristled when I arrived. I was very young and vulnerable, and it was awful.