Liam Gallagher found filming the new Oasis documentary "like therapy".
The 44-year-old rocker was forced to relive the past in interviews for 'Supersonic' and director Mat Whitecross says the outspoken star found an unexpected benefit to their on-camera sessions.
He recalled: "Liam kept saying, 'This is like therapy I never had; I'm going to come back next week'. I kept on saying we should pretend the film's not coming out!"
Liam and his older brother and former bandmate Noel Gallagher - who have rarely spoken since their row which split the group in 2009 - wouldn't be interviewed together for the film, but the director found that to be beneficial.
He explained to the Independent: "When I look back on the archives of them together, it's very funny and scandalous, but it's relatively superficial. When we got them separately, we could dig deeper, revisit stuff and not worry one of them might walk out at any moment."
For Mat, who was a huge Oasis fan, the group's music played a big part in the film but he would only include a song if it was relevant to the story he wanted to tell.
However, because of licensing costs, he was unable to include the group's cover of The Beatles' 'I Am the Walrus' in the finished documentary.
He laughed: "We had a list of every song on the wall. The golden rule was it's not enough for a song to be good - it's got to tell a story.
"I wanted their version of 'I Am the Walrus' in there so we could start talking about The Beatles' influence. The music supervisor went, 'Let's put it this way: you can have the entire Oasis back catalogue or 'I Am the Walrus' - which is more important to you?'
"I was like, 'f**k it, I'll take that one out'."