"They're my identity", says reggae superstar Bob Marley, quizzed at the height of his fame about his trademark dreadlocks.

Yet the longer Kevin Macdonald’s exhaustive, definitive doc goes on, the more Marley’s popular image as ganja-smoking Rastaman dissolves into a more complex picture.

Macdonald assembles his film with admirable simplicity, as urgent yet mellifluous as Marley’s music.

Beginning at the beginning and ending at the end, Macdonald interviews everybody, from Bob’s first teacher to the nurse at the German cancer clinic where Marley spent his last months.

The involvement of friends, family and colleagues skews sympathy, but there is such a multiplicity of voices (refreshingly candid ones) that the mosaic reflects Marley’s contradictions: the shy, serious musician who became a prophet on-stage; the polygamist so respected by his wife, Rita, that she helped to kick out the groupies when he was done.

Macdonald has one rule: you had to be there.

So Bunny Wailer, chief witness to the birth of Marley’s spiritual slow-jam, vanishes once he has recounted their falling out over fears of a creative sell-out. The canvas widens with Marley’s increased fame, his political influence sparking assassination attempts and revolutions.

Macdonald reassembles archive footage into thrilling sequences closer to his previous forays into ’70s politics, One Day In September and The Last King Of Scotland, than chin-stroking MOJO territory.

Yet incredible concert performances and recordings maintain focus on the universal reach of the music.

By the time ‘Redemption Song’ signals a moving account of Marley’s premature death, you’ll be a wreck.

DVD Extras:

• Featurette 
• Concert footage 
• Interview