Well, suddenly, the tone of the discussion has changed. It has moved on a bit from the starting point, but it's introduced some interesting thoughts - which is all I intended to provoke.

One misunderstanding from a few posts back: that punk bands would not want to see themselves labelled "folk". In fact here are few people reading this who would not find the Skids' solo unaccompanied rendition of And the Band Played Waltzing Matilda to be a good, respectful and sincere rendition of this great song.

Apart from the misguided introduction of some melancholy keyboard "choir" in the last verse or so (it was a new "toy" back then) it would pass muster in any folk club I've ever visited, even on the nearest meeting to Armistice Day. But the Skids would have called themselves punk.

The best answer to my initial question is the one referring to Terry Pratchet's answer to the literature question. Regardless of the subject material, and the origins of the singer, and his close association with the audience, and the audience's familiarity with the working environment described in the song, it is unlikely to be remembered in 50 years' time. That is why it is not a folk song.

I think a song becomes a folk song when the singer and the audience have no idea who wrote it, and no reason to care, and they just sing it because they enjoy singing it. Anything else is, at best, no more than "in the folk style" or "sharing some of the characteristics of a folk song".

I have written a few tunes over the years. Any one of them is broadly within the generic traditional style. Plenty of people have asked me where I learned them. They will only be starting to be folk tunes the day I walk into a pub I've never been into before and a complete stranger is playing one of them. I do not expect this to happen, but it would be hugely satisfying if it did.