Peter Bellamy was apparently convinced that this was written by an actual highwayman, the details being so vivid and specific, but it ain't necessarily so - and not just because armed robbers aren't usually noted for their literary skill*.

The first** time I read the Gospel of John I was taken aback by how vivid some of the descriptions were - very odd to a modern eye, when you think how long after the event John is believed to have been written. An authority I consulted*** said that ideas of veracity were different then - if vivid details 'sold' the story better, vivid details it would have, even if you had to imagine what they might have been. Something similar applies to what seem like really vivid details in this song - "Lord Arkenstone", "the Earl of Warren" and the rest, not to mention Valentine O'Hara himself. Why make up a highwayman called Valentine of all things? Well, why not?

*Apart from Bonnie Parker
**and only
***my Mum