This pleasantly unpretentious 2019 doc traces the origins the song "Rock Island Line" and through it sees the skiffle phase and the birth of the massively influential British rock acts of the 1960s. There's a nice amount of detail here and crucially, those being interviewed are either archivists, relatives or those who were there at the time. Bragg isn't a showy host here and when finally we see an archival clip of Lonnie Donegan, the skiffle king, you can see an even clearer line between Skiffle and punk, and the politically aware agitational acoustics of Bragg himself. They sound identical.