Noel Gallagher knew Oasis were going to be the "biggest band in the world" the day after he wrote 'Live Forever'.

Never-before-seen footage of the Britpop group performing the 1994 hit from their acclaimed debut studio album, 'Definitely Maybe' - which the 54-year-old guitarist penned the year he formed the iconic rock band with his now-estranged brother, frontman Liam Gallagher, in 1991 - at their iconic 1996 Knebworth concert has been shared ahead of the release of the documentary 'Oasis Knebworth 1996'.

Noel commented in the clip: "We were a pretty decent band the night before I wrote 'Live Forever' but it was indie music. The day after I wrote 'Live Forever', we were gonna be the biggest band in the world. I knew it."

The 'Some Might Say' hitmakers - who split in 2009 due to tensions between brothers and bandmates Liam, 48, and Noel - will mark the 25th anniversary of their two record-breaking shows at Knebworth Park with new film, and the production will include more unseen concert and backstage footage, as well as interviews with the band members and event organisers.

Liam said: “Knebworth for me was the Woodstock of the 90’s. It was all about the music and the people. I can’t remember much about it, but I’ll never forget it. It was Biblical.”

Noel added of the shows: “I can’t believe we never played 'Rock ‘n’ Roll Star'!”

The chart-topping band played to 250,000 fans across two days in August 1996.

The announcement of the Knebworth shows prompted four per cent of the population to apply for tickets and almost 25 years later, the gigs remain a milestone for rock 'n' roll in Britain.

Noel previously described the upcoming documentary as a "fantastic snapshot of a bygone era".

The 'Wonderwall' songwriter promised fans that the project would be "really great".

He explained: "There’s a lot of stories in the press about it being a film company for a biopic, which of course it’s not.

"The gig Oasis did at Knebworth is 25 in August and back in [1996] we’d filmed it all really professionally with loads of cameras, we had cameras on the trains with fans.

"But for one reason or another, the film never came out but as it’s the anniversary coming up, we’re going to be releasing it now.

"I’ve seen a tiny trailer of it and it’s a fantastic snapshot of a bygone era before the internet. It’s great, really great."

For tickets for screenings of the documentary, which is released worldwide on September 23, head to www.oasisknebworth1996.com.