Becoming Led Zeppelin is a new authorised documentary that tells the "untold story" of the band, who despite achieving global influence and legendary status, are difficult to define.

Rock's mightiest anthems, and the tales surrounding them, tend to be continually replayed – and sometimes, their power fades over time. Since their 1968 formation, though, Led Zeppelin's legendary status, and mythology, has particularly endured. The British quartet – driven visionary guitarist/producer Jimmy Page, extravagantly swaggering vocalist Robert Plant, and the poetic powerhouse rhythm section of bassist John Paul Jones and drummer John Bonham – have remained instantly recognisable and globally influential, yet tricky to pin down. Their multi-million-selling catalogue is laced with blues, hard rock, folk fables, African, Asian and Latin grooves, macho bombast and avant-garde flair. They gained a rep for scandalous excess, while mostly shunning the press – but now Becoming Led Zeppelin, their first officially authorised documentary, promises to capture the band's "untold story" for posterity.

This film's long-awaited cinema release follows a "work in progress" screening at the Venice Film Festival in 2021. Becoming Led Zeppelin also forms a natural progression for filmmakers Bernard MacMahon and Allison McGourty, following their award-winning 2017 doc series, American Epic, traced the history and impact of America's earliest roots music recordings.

"We wanted to do a film that would pick up the next era," MacMahon tells the BBC. "Rather than looking at 100 acts, like we did with American Epic, we looked at whether there was one act that carried that music through from post-World War Two to the 60s and 70s, and were the embodiment of that final stage of 20th-Century music – and we realised it was Zeppelin."

Getting Led Zeppelin's surviving members on board involved a meticulously fine-tuned pitch – but it was also pivotal that Page, Plant and Jones were fans of MacMahon and McGourty's previous work; American Epic documented their own musical heroes. "Becoming Led Zeppelin wouldn't have happened without American Epic," admits McMahon.

Still, Plant warned the film-makers: "I don't think this film can be made, as we didn't do any TV, and Peter Grant [Led Zeppelin's formidable manager, who died in 1995] would eject audience members with cameras from the venues, rip out their film and smash their cameras, so there isn't any footage of our concerts from those years."

In fact, Becoming Led Zeppelin features two hours of painstakingly sourced archive material, personal photos and performance footage (schoolboy Page playing in a skiffle band; teenage Jones as a church organist; both becoming accomplished session musicians on '60s pop hits) alongside individual new interviews from Page, Plant and Jones. Bonham's death in 1980 (from pulmonary aspiration after heavy drinking) would lead to the band's split – yet he is also surprisingly present here, sounding jovially down-to-earth on a previously unheard audio recording.

As a child, MacMahon had "discovered" Led Zeppelin via a book charting the band's rise to fame. "It felt like the American Epic stories, in that it's very relatable: these are four kids, pursuing this........

© BBC