Steeleye
They covered "Thomas the Rhymer", too. I think it was on the Now We Are Six album, around the time they switched to Chrysalis Records and came under the influence of Ian Anderson (Jethro Tull), and vice versa.
Here's a couple of comprehensive fan sites from my bookmarks:
Reinhard Zierke's English Folk Music Website
Unofficial Steeleye Span Homepage
I saw them on the Now We Are Six tour... must've been 1974 (?), or thereabouts. Tony will recognize the venue, one of Philly's best: The Academy of Music.