Oh it's very late in the day, but I'll put in my two penn'orth.

Bert Lloyd, I believe, was enamoured of the Lydian Mode. He gave it some attention in his Third Programme programme about Bartok (Bartok as a Folklorist? - I'm relying on recollections of more than 50 years ago for all of this). His version of Lucy Wan had a tune that was quite clearly - deliberately you might even say - Lydian. It used only the first five notes of the Lydian scale, which served to emphasise the raised fourth.

In the late 1960s I heard Bert sing Lucy Wan at least a couple of times, one of them in our folk club in the Royal Sovereign, Kirkstall, Leeds (long since demolished) around 1967. It was in the Sovereign that I asked from the audience where the tune was from, and he fudged his reply, and henceforth I assumed that he'd made it up.

Nothing wrong with that, and I'd go along with Martin Carthy - what we've ended up with is a chillingly memorable song. Provenance is secondary.