Campbell played during the new record's initial sessions before he stepped back to undergo surgery for Hodgkin's lymphoma. And he says when he was involved, the tracks they worked on were purely rock songs - although that might not be the case now.

He tells Canadian radio station Free FM: "Well, it's never finished until it's finished, but when we first started playing we did track as a band, and when we do that, we tend to write more rock songs. The first four or five tracks we cut were on the heavier side, but I have no idea if they will actually make the grade.

"The way Def Leppard records work, the last guy in the studio gets to have the final word. So who knows? I'm not gonna be there because I have too much medical stuff going on. I'm kind of done at this stage. There may be a final session in January or February that I'll not be party to, so I have no idea what the final thing's gonna be.