Anyway I like it better than having him pin her to the wall, which is the sort of thing Zorro would do. Decapitation is far more medieval. Martin Carthy has him cut her "paps" off- which is a little too horrible.
Matty Groves is Child Ballad #81. Everyone sings it a little differently, with varying words and varying tunes- which is how things should be with the folk tradition. The eponymous hero is also known as Little Musgrave. And the man who kills him is variously Lord Donald, Lord Barnard, Lord Daniel and so on. I like him best as Lord Barnard- because Barnard Castle is a place you can find on the map (I understand they have a really good branch of Specsavers there)- and I like to think of the story having once actually happened in an actual place. The wife never has a name of her own- in spite of her being of "noble kin"- and this tells its own story.
The Ballad of Matty Groves/Little Musgrave is a tragedy- in the purest sense of the word. Everyone in it acts honorably and bravely, according to their wyrd. They do what they have to do- and the trap unforgivingly snaps shut on them. Even the servant who snitches on the lovers is doing the right thing according to the strict dictates of the feudal system in which he is embedded.
My favourite version is Fairport Convention's- because it's stripped back to essentials- and is not only a great song but a great poem.