A 1966 photo used in the documentary “Lambert & Stamp” shows Chris Stamp, left, and Kit Lambert. As aspiring filmmakers, they chanced into becoming managers of the Who, an iconic British band. (Personalities/AP)

Full disclosure: I was a teenage Who fan. From the Roger Daltrey poster on the bedroom wall to ill-advised road trips to see the band in far-flung venues throughout the greater Midwest, I considered myself a hard-core fan in the 1970s, as militant in my admiration for the British foursome as some partisans were about the Beatles and the Stones.

But even in the deepest throes of my devotion, I had no idea how cardinal a role Kit Lambert and Chris Stamp played in forming the Who, a lacuna in rock-and-roll creation mythology that is corrected by “Lambert & Stamp.” In this illuminating documentary, filmmaker James D. Cooper does cultural history a service in restoring the duo to their rightful place as the Who’s fifth and sixth — that’s according to Daltrey — members. What’s more, through some astonishing archival footage and perceptive commentary from Who guitarist Pete ­Townshend, the filmmaker puts the band in its complicated context as both reflector and creator of the postwar British teenage gestalt.

Lambert and Stamp were unlikely comrades. Lambert, son of classical composer Constant Lambert, grew up in the English aristocracy, attending Oxford and serving in the military. Stamp — described by brother Terence as an East London tough — was the son of a tugboat captain, a kid without direction until he fell under the spell of the French New Wave in the 1960s. (Terence, of course, would become one of the avatars of England’s own cinema of the swingin’ ’60s.)

When Lambert and Stamp met as aspiring filmmakers at Shepperton Studios, they hit on the idea of making a movie about a rock-and-roll band as it morphed from unknown to famous; while searching for their protagonists, they visited a throbbing, cramped nightclub where a group called the High Numbers was playing and immediately recognized their destiny. They would eventually make a film, they decided, but for now they would also manage the band.

Drawing on interviews with Stamp — who died in 2012 — and Townshend and Daltrey, as well as with friends and early witnesses to the Who’s ascent, “Lambert & Stamp” in many ways hews to the conventional rock-and-roll origin narrative, including Spinal Tap-ish pretensions and self-indulgent excesses. (Lambert, who died in 1981, appears by way of old interviews and news clips.)

But what sets this story apart is how the title duo — as disparate as “chalk and cheese,” according to one crony — cannily masterminded the Who’s collective persona, itself a volatile mix of clashing temperaments and personal styles, to create an entity that resonated with the disaffected, sharp-dressing Mods who flocked to the earliest shows. When Townshend spontaneously destroyed his guitar during one performance, the gesture became one of the band’s many subversive signatures; the guitarist himself recalls spotting a natty outfit on a fan in the crowd, then adopting the look for his next show. “You don’t just market to them,” he says, recalling the Who’s transactional relationship with its audience, “you market them.” (It was Stamp’s idea to add the stutter in “My Generation,” an homage to the rampant amphetamine use of the era.)

While Lambert and Stamp perfected the Who’s stagecraft and publicity strategy, they also helped Townshend with his songwriting, with Lambert calling on his classical-music roots to introduce the guitarist to composers such as Henry Purcell. The result, in 1969, was “Tommy,” a full-blown rock opera that saved the Who from breaking up and created not just an ambitious new form, but also newly minted millionaires.

More money, more problems: Lambert and Stamp’s partnership with the band began to fray in the 1970s, exacerbated by Lambert’s drug abuse and other issues. The narrative flags and becomes a bit fuzzy during this section of “Lambert & Stamp,” and Cooper never quite makes clear who did what when. An interview conducted with Stamp in 2008, when he attended the Kennedy Center Honors with recipients Daltrey and Townshend, begins to sound and feel like a late-night conversation that’s fun at the time, less so in the retelling.

Then again, by that time he’d more than earned the right to keep his interlocutors awake. As “Lambert & Stamp” reveals, Lambert and Stamp played a crucial, heretofore largely hidden, role in shaping pop-culture history — not to mention the noisy, visceral, rebellious zeitgeist of th-th-th-their generation.

R. At Landmark’s E Street Cinema and AMC Loews Shirlington 7. Contains brief profanity, some drug content and brief nudity.
117 minutes.