Alan Yentob traces the guitar from an ancient Middle Eastern relative of the lute to the instrument slung around the necks of Bill Haley and Elvis Presley, asking how it became the world's most popular instrument. The three-part series starts with the acoustic guitar's rise, then follows its spread through skiffle, rock and roll, and beyond, mixing archival performance footage with new interviews. Bert Weedon, whose "Play in a Day" method taught a generation of British guitarists, explains the instrument's postwar boom, while Pete Townshend and comedian Bill Bailey talk about what the guitar does on a rock stage. Flamenco player Paco Pena and classical guitarist John Williams widen the story past pop and rock, showing the same six strings carrying entirely different traditions. Yentob treats the guitar less as a fixed object than as a shape that keeps getting reinvented, tracing how one design ends up equally at home in a flamenco club, a symphony hall, and a stadium.