The unlikely partnership of Kit Lambert and Chris Stamp, the managers of the Who in their early days, is the subject of a new documentary. 'Lambert & Stamp' had its premiere at the Sundance Film Festival in Park City, Utah earlier this week.

The movie, which was directed by James D. Cooper, traces the story of the duo, who met in the early-'60s working on film crews in London. While looking for a band for a project they conceived, they discovered the High Numbers, who soon reverted to their original name, the Who. They were so blown away by the group that they abandoned the film and became the band's managers.

"I think it's the greatest untold story in rock," Cooper told Rolling Stone. "It's a relationship played out through musicians on the rise to mega stardom, and how the dynamics of that relationship reinforce one another."

Cooper had the participation of Pete Townshend, Roger Daltrey and many others close to the band, including Chris' brother, actor Terence Stamp. They discuss how Lambert, the son of a composer, pushed Townshend to write more complex material than the standard three-chord fare, resulting in the mini-opera, 'A Quick One (While He's Away)' and, later 'Tommy.'

By 1975, the two had been forced out and replaced by Bill Curbishley. Lambert was fired in 1971 and died 10 years later. Stamp held on until 1975. He passed away in 2012 from colorectal cancer.