Duff McKagan says Guns N' Roses' first classic line-up reunion show at the Troubadour in 2016 was "nerve-wracking".

Guns N' Roses

Guns N' Roses

The 'Welcome to the Jungle' group's frontman Axl Rose performed with bassist Duff and guitarist Slash for the first time in 23 years at the West Hollywood venue, before they headlined Coachella festival later that month, and the concert turned into chaos as Axl ended up breaking his foot in six places by the third song after slipping on a monitor and his microphone.

Recalling how it all unfolded, Duff told Planet Rock: "I've gotta say, and I can't really say it enough -- just the fact that we got together way before that and communicated and talked would have a lasting effect on me personally.

"Then [we thought], 'Okay, well, [let's] try some gigs. Coachella wants us to play. That's two weekends.

"We can do that. Why don't we do something on April 1st, April Fools' Day? Announce it maybe with a question mark.'

"But Axl, third song in, breaks his foot at the Troubadour.

"A nerve-racking thing that show, 'cause it was first time back. And then there was a monitor thing.

"I saw it. He's pretty athletic too -- he can bounce around and do stuff.

"He slipped on that thing, and on his mic, he goes, 'I think I broke my foot.'

"But he got on and finished the set.

"And I'm, like, 'Okay. Maybe he sprained it.'

"No, but he broke his foot in six places.

"But we continued on -- he wanted to continue on. I think it was a call to arms for him."

Axl then performed the rest of their shows in his own metal throne and it was then that Duff realised his bandmate had "become a master" of his craft through his rigorous warm-up routine, including going to the gym, which he admitted he hadn't noticed before then.

He added: "Singing those songs sitting down ... I don't know if anybody out there listening is a singer ... I realised at that point, the guy has become a master.

"His warm-up regime -- an hour-and-a-half warm-up thing -- and being able to sing those songs sitting down.

"And then his warm-down routine.

"He'd become a master. And maybe he always was, and I didn't notice it before.

"But the amount of work he puts into a gig -- it's gym, warm up for an hour and a half, do a three-and-a-half-hour show, warm down ... I'm already in bed. But, yeah, for it to go ... We did 159 shows, I think."

The band's 'Not In This Lifetime Tour' featured the classic line-up, Slash, Duff, Axl, plus Richard Fortus, Frank Ferrer and Dizzy Reed.

The classic line-up are set to enter the studio to work on their first album together in 11 years later this year.