IN 1970, four lads from Birmingham released their debut, self-titled album to watch it hit the top 10 in the UK and later the top 40 in the US. Black Sabbath had arrived, their mix of dark, menacing rock and mythic lyricism laying the foundation for heavy metal and influencing bands at the heavy end of rock ever since.

The quartet – Geezer Butler, Tony Iommi, Bill Ward and Ozzy Osbourne – knocked out nine albums before internal pressures saw the departure of frontman Ozzy and his replacement by Rainbow singer Ronnie James Dio.

With Dio and then new drummer Vinny Appice on board, the band recorded two more albums – Heaven and Hell (1980) and Mob Rules (1981) – and a live album that revitalised the band’s reputation before the tempestuous act again sundered into years of instability.

Now a collection of tunes celebrating the Dio years – including 1992’s shortlived reformation and Dehumanizer album – has been released with three new songs, and the band is on the road for a 12-month tour labelled Heaven and Hell.

For bassist Geezer, it’s all a pleasant surprise, really. Speaking from his home in Los Angeles, he says the band is enjoying a longevity no one ever expected.

“You didn’t even think about it back then,” he says. “At the age of 25 you were considered old hat and you’d go get a proper job. We were 19 when we founded the band and thought we’d only go five years.

“The tour’s going really well. The best part is that it was unplanned. We just took it as it came. If you’d asked me a year ago, I wouldn’t have said we’d be doing this. We didn’t have time to think of the negatives, and when we got going, there weren’t any.

“I’ve never heard Ronnie sound better. We’re all playing the best we’ve ever played; I think because I haven’t played any of it since 1997 so it’s fresh to me too, we’re not just going through the motions.”

The tour came around after plans were put in train for the Dio Years collection, he says.

“The record company wanted to know if we had any unreleased material for a bonus and we said we didn’t, but we could write some stuff. So Tony and Ronnie got together and then I came in and did the bass and Vinnie came in and we ended up talking about touring to back the collection. It was going to be a six-week tour but it turned into 12 months.

“We’re pacing ourselves properly this year, four weeks on and then taking a couple of weeks off. Obviously we’re not young any more.”

He says it has been refreshing to team up with his bandmates again after 15 years, and that he’s surprised to find a young generation appreciating their music.

“So many metal bands say Black Sabbath is an influence, they want to see what it’s all about. There are 14- and 15-year-olds who know all the lyrics to our songs, songs that were written in 1980, before they were born.”

As for the chances of the original line-up touring Down Under, he says. “I’m not going to say no. I didn’t think we’d be doing this tour. I’d like to do a final tour, take the original line-up to the places we didn’t get to visit, and Australia and Japan. A final world tour and that’d be it.”