They were quizzed endlessly and one wrong answer could have blown the lot. The makers of Becoming Led Zeppelin relive the tactics – and cups of tea – that got it green lit

Bernard MacMahon says he knew he was taking a massive risk. The Irish-British film-maker and his Scottish partner Allison McGourty had spent 10 months researching a film about that massively successful but elusive rock band Led Zeppelin. They put together a storyboard, listened to every interview they could find, and started to dig out archive film to tell the story of the band’s early years in the late 60s.

That was when Jimmy Page, a successful session guitarist, joined the Yardbirds, then wanted to create a band of his own. He signed up John Paul Jones, another virtuoso session star, and two little-known West Midlands musicians: the wildly inventive drummer John Bonham, and singer Robert Plant. Overlooked in Britain, Led Zeppelin found fame in America, where they were attacked in the music press but became celebrities through their live shows, without the help of the media.