Following the failure of his revolt, Neville of Westmoreland flees to Scotland and is taken to Hume Castle. Neville at last sails for Seville, and is given office by the queen. He fights the heathen and is victorious, and receives various rewards
For the background to this song, see the notes on The Rising in the North" [Child 175]; also "Northumberland Betrayed by Douglas" [Child 176].
The song itself is almost pure fiction; the only truth is in the introduction, in which Neville flees to Scotland, goes to Hume, and sails to the Continent. (In reality, he spend the rest of his life in exile in Flanders.)
One suspects that this story somehow got mixed up with a romance. I have this odd feeling the legend of Guy of Warwick is involved (though the only clear similarity between the two is that both fought pagans); Guy was not a Neville, but the most famous Earl of Warwick in English history was of the Neville family (though a cadet branch). - RBW