Peter said that 'Yarmouth Town' was the first song he ever 'collected', and that he got it from Peter Bullen (of Norwich?) who he knew in his Norfolk days. Bullen said that he'd learned it from his grandfather. This may be so, or it may not: it is probably impossible to find out now. Bellamy also got 'Fakenham Fair' from him, it seems.

There is some brief discussion of this in thread Lyr Req: Yarmouth town (2001, revived in 2007). A more extensive discussion took place on the Ballad-L list in 2005, which you must have forgotten about, Steve: it was you who started it. You were not the only one who suspected that all might not be what it seemed; I think that I remained agnostic on the subject, though I'm inclined to think it a quite recent composition, whoever was actually responsible for it.