Butler tells Armi Official: "I like Mastodon, but I'm not sure how big they will become. And I like Royal Blood, but I'm not sure they could maintain the longevity required.

He adds: "The music industry today is unrecognizable from when we first started. I think it's harder than ever to break through the success barrier, especially for rock and metal bands.

"It's very hard to make a good living out of music for new bands, especially with the access to the internet these days, having so many people posting their videos online.