He told Canadian TV host George Stroumboulopoulos on The Strombo Show that he turned it down because he didn't want to be typecast.
Plant says, "I started that [crap]. Go back to ‘Immigrant Song,’ Led Zeppelin being part of a cultural exchange in Iceland with the Icelandic government, so they didn’t really know what they’d invited onto their little island, and so on the way back on the plane I started thinking about…because I love Western European history, you know from maybe the Bronze Age up through all the old religion, the great sort of when we were really in touch with our earth, and so the Viking thing was obviously, so that whole idea of playing in Iceland and and experiencing this amazing landscape and people, so yeah I’ve got a lot to answer for already because I’ve never seen so many bands with double-bladed axes and looking like that, you know. It was they could have all looked like Soft Cell, you know, something like that."
He adds that he doesn't "got time to grow the beard really, so no."