"So that I now have 2 good reasons for not treating the Leniham version as an independent line:)

1 Odd that after over nearly 70 years of folkloric writing claiming Irish origins a song representing a whole line should suddenly appear

2 The singer said his version came from America."

So, let's get this straight:

In Point 1, you're suggesting that Tom Lenihan's song is a fake, presumably engineered by the "folk movement" to validate the sleeve notes of a 1960s Folkways LP. Even in our age of conspiracy theories, this is fantasy on an epic scale.

Point 2 has already been addressed by Jim Carroll. Athough I don't share Jim's scorn for deskbound research (there's plenty of good info to be accessed from a computer, as this discussion demonstrates), I'd have expected a serious researcher to place more credence in the testimony of a field worker who was actually there, and knew the singer for 20 years.

I can accept that Lloyd collated his own version of the song, and that the sleeve notes in question are flawed. But in trying to extend your argument to claim that all the instances of 'St James' in versions of what I'd better call Roud 2 derive from the jazz standard, you are ignoring the facts. These are that:

(a) An oral version mentioning St James but clearly of the Unfortunate Lad / Rake / Sailor Cut Down family was collected 10 years before 'St James Infirmary Blues' was recorded.

(b) Several other independent oral versions mention St James but otherwise are completely dissimilar to the jazz version. If the latter had influenced the former you would expect more common text, but they don't even use the word 'infirmary'.

I don't know whether it's a good idea to go into The Dying Cowboy / Tom Sherman's Bar-room strain of the song here (there's already been a Mudcat discussion of that one), but that goes back to at least 1916, so it seems that the jazz standard took the bar-room location from there - if not much else.