Maybe they meant 'Britain'! Don't think so, After Edward 1 went motoring through Wales the subsequent Statute of Rhuddlan lost the Principality its independence and it became effectively an annexed territory of the English crown around 1283AD. England had several invasions of Scotland prior to the treaty of Berwick around 1357, where independence was recognised up until the act of union.(I think) Richard 2 reigned 1367-1400. The bard was quite a bit later on the scene.
So a bit of poetic licence as far as the landlocked Scottish border was concerned.