Jack, are you sure that the Banks of Devon is the same tune as Streets of Laredo? I just listened to a Youtube of Karine Polwart singing the Banks of the Devon, and it didn't sound the same at all.

Wikipedia says that Streets of Laredo shares a tune with Spanish Ladies, which I would have thought would be even better known in the early 19th century. But I listened to a few versions of that on Youtube, and that didn't sound the same either.

The Bard of Armagh does seem to be the same tune.