The verdict on David Bowie’s first demo for the BBC with his mid-60s combo The Lower Third was disastrous. “The singer,” went the report, “is a Cockney type but not outstanding enough.” You can almost hear the author wiping his lorgnette disdainfully on his smoking jacket.

The band’s underwhelming Kinks and Who knock-offs were woeful enough, but it was their misbegotten version of the Mary Poppins clunker Chim Chim Cher-ee that tipped BBC bosses over the edge. The cover, the report charged, “kills the song completely”.

For those of us for whom Bowie remains the last word in cool, pick ’n’ mix musical genius, avant garde gender-bending and transgressive self-reinvention, there were some pretty tough moments in David Bowie: Finding Fame (BBC2). I had steeled myself for his novelty single The Laughing Gnome, with its unacceptable animation and its Bernard Cribbins-and-Benny Hill-on-helium-impersonate-Pinky-and-Perky vocals. And yet, when the back story of how it was made was related, I contemplated the middle distance with rueful mien.

Then there was the miming. My God, the miming. Even the dance/mime teacher Lindsay Kemp was not impressed by the spandex-stretching routines Bowie inflicted on early audiences. “He was,” recalled Bowie’s one-time lover, not unpleasantly, “a lot of shit.”

For all that, Bowie’s early years revealed him as a heroic outlier, a proto Gok Wan persuading a series of unreconstructed white English blokes in the band to free their minds and wear makeup. In the back of the ambulance that served as The Lower Third’s tour bus, Bowie argued they should emulate groovy mod bands in London with their sharp suits, amphetamine intensity and makeup. “Graham [Rivens, the bassist] turned round and said: ‘Fuck that’,” recalled guitarist Denis Taylor. Which is why the world has never heard of The Lower Third.

‘When they realised how many girls they could pull while looking otherworldly,’ recalled Bowie, ‘they took to it like a duck to water.’ Photograph: PA

There was another fabulous moment in which Bowie induced members of his band Riot Squad to retool the Velvet Underground’s Waiting for the Man. They performed a sort of homosexual conga on stage while, unless I misheard, Bowie sang: “I’m just waiting for a good friendly behind.” Sweet, but probably not what Lou Reed meant at all.

Later, Bowie convinced Mick Ronson, Woody Woodmandsey and Trevor Bolder, who have – I would submit – the most hetero names in the glam rock pantheon, that not only should they stretch silver satinette over their beer guts but conceal their stubble with foundation. Only then could they become the Spiders from Mars to his Ziggy Stardust. “When they realised how many girls they could pull while looking otherworldly,” recalled Bowie off-camera, “they took to it like a duck to water.”

But how did the boy from suburban Bromley mutate into lubricious alligator, Major Tom, funky thigh collector, pierrot junkie, not to mention squaddie amusingly buried up to his neck in sand by Japanese captors in Merry Christmas, Mr Lawrence? One theory, advanced by his superbly named cousin, Kristina Amadeus, was that he was always trying to please his mum, Peggy, who came across here as a very cold fish indeed. Childhood friend Geoff MacCormack, writing to Bowie after her death, said he thought she never approved of him. “She never quite took to me either,” Bowie wrote back.

I wanted to learn more about his half-brother Terry, who Bowie here recalled as a rebel outsider and the catalyst for his escape from suburbia. It would have been intriguing to hear his early song Bewlay Brothers, in which the laughing gnomes make a comeback. “Please come away, just for the day,” they chant. It is as if little David is singing to his lost sibling who, we learned, ended up hospitalised with schizophrenia, while David made a career from slipping into and out of different personae – as if applying Oscar Wilde’s principle: “Man is least himself when he talks in his own person. Give him a mask, and he will tell you the truth.”

The mask did slip once. Bowie’s first love was Hermione Farthingale, with whom he played in a band called Feathers. In contemporary footage, this wan ballet dancer was a dead ringer for Bowie, as if glam Narcissus had fallen for his feather-cut Echo. But like Ziggy Stardust, she had to break up the band. And worse, break David’s heart. In 1969, she left him to dance in an MGM musical called Song of Norway, while he made her a muse (“It’s a godawful small affair,” he sang on Life on Mars, “to the girl with the mousy hair”).

Hermione, now a yoga and pilates instructor in Bristol, recalled him with fondness, while we heard audio of her late lover remembering: “I didn’t get over that for such a long time, it really broke me up.” Bowie was, for once, not master manipulator of sound and vision, not virtuoso of a thousand disguises, but something sweeter: unguarded boy with a broken heart.