If, as that multi-part BBC2 documentary maintained, there were seven ages of 20th century rock music, then The Who are the bridge between eras two and four.
Essentially they were a West London beat group, forged in the same crucible as the Stones and the Kinks, who enjoyed a brief mid-1960s fling with psychedelia, fashioned the first "rock opera" (Tommy, 1969), and emerged blinking into the post-Woodstock glare as the world's heaviest exponents of over-amplified Sturm und Drang.
What allowed them to sustain this impetus into the Seventies and beyond was the song-writing (and organisational) skills of guitarist Pete Townshend. Without him, The Who would scarcely have existed. With him, the ride would never be easy, and if some of the tensions that undermined the band can be ascribed to the three other founding partners, quite a few are down to Townshend.
Most rock memoirs - and Who I Am is a winningly candid example - weave variations on the chicken-and-egg debate. Does the music business damage the personalities of the people who work in it, or does it merely attract people with damaged personalities and damage them further? Here, nature and nurture zealously combine.
Townshend was an archetypal mixed-up Sixties kid. Drummer Keith Moon and bass player John Entwhistle were career hedonists, who paid a girl $100 to infect Townshend with gonorrhoea on the premise that he was too strait-laced around the groupies. Vocalist Roger Daltrey, outwardly the sanest of the four, was a hard-boiled, insecure Mod from Acton, who knocked his guitarist out cold after waiting 48 hours for stage tapes of their 1973 album Quadrophenia to arrive at the recording studio.
Having established the band as early 1970s behemoths, Townshend runs through the full menu of rock-star trauma, finds God, goes manic-depressive and stages titanic drinking contests with the roadies, while striving for a brand of self-expression that will reveal "the essence of rock itself". Moon auto-destructed in 1978, with Entwhistle following in 2002.
"Pop music was evolving, becoming the barometer for a lot of social change," writes Townshend of the Sixties maelstrom. There are several fascinating moments when he picks up the pop-sociology baton first wielded by the late Ian MacDonald in his Beatles book Revolution in the Head and looks as if he might give it a flourish of his own, but not nearly enough. For all its candour, Who I Am has to be filed under "missed opportunity".