>> My own wild guess: there were scarcely any "protest folksongs" in the 19th C. <<

There were plenty of protest broadsides. No-one is suggesting that Bert Lloyd or anyone else made up 'The Cotton Lords of Preston', or 'Handloom v Powerloom', or 'The Miners Lockout' (all from Harry Boardman's repertoire, of my fond memory). See also 'A Touch on the Times' and 'Victoria's Inferno'.

The interesting question for me now - having been really turned on by all that stuff in my teens - is whether those industrial broadsides had any currency in oral tradition. For the reasons Nerd cites, we may never know whether 'The Cotton Lords' was ever a folksong in the sense that, say 'Barbara Allen' was, although by giving his chapter in Folksong in England on The Industrial Songs equal billing with the chapters on Ritual Songs, Ballads and Lyrical Songs, Bert Lloyd was implying that.

Which is why Beckett Whitehead and the other source singers for 'Industrial Folksongs' are so important. If Whitehead did indeed sing 'The Four Loom Weaver' to MacColl, that would be evidence that the old broadside piece had indeed exerted a hold on the popular imagination that survived well into the twentieth century. As a song.