The stars pay homage to 87-year-old blues guitar giant BB King in this thorough biographical doc, which features Eric Clapton, Keith Richards, Bonnie Raitt, Bobby Bland and Buddy Guy among his few living peers. With its gooey Morgan Freeman voiceover and yards of praise, it would be easy to dismiss this as hagiography, but mister Riley B King deserves every paean and we’re never likely to see the likes of his journey again. To its credit, Jon Brewer’s film digs deep into the roots, taking us back to Indianola, Mississippi, where young Riley ploughed fields in his childhood. Such grinding poverty and racial segregation explains his subsequent endless touring to largely white houses – audiences introduced to the blues by Clapton and The Stones who revered original purveyors like King. A smidgen more music would have been nice, but the interviews are affectionate and illuminating, and King remains the soul of modesty. In the music business, ‘legend’ is an over-used word: see this and understand what it means.