If you’re going to be a sidekick, be a sidekick to the best. Mick Ronson was not just one of the finest guitarists of a generation but also the creative spur to singers as diverse as Bowie, Morrissey and Dylan. Humble and unassuming off-stage and a whirlwind of riffs and attitude on it, Ronson was the kind of catalyst who drove his bandmates onto better things. This elegant documentary, directed by Jon Brewer (B.B. King: The Life of Riley, Nat King Cole: Afraid of the Dark), narrated by his old mucker Bowie and featuring exclusive access to never-seen archives is a handy introduction to the engine room behind a handful of the twentieth century’s best songs.