If you’re one of those people who think superannuated rockers from the late 1960s have no business going on tour, you’ll get a kick out of Neil Young’s new film CSNY: Déjà Vu. It’s nearly 40 years since the heyday of the folk-rock super-group Crosby, Stills, Nash & Young, and this documentary charts the reunion of the old gang in 2006 for one more road trip.

Musically, as Young admits in a voiceover, the early part of the tour was “a bit rough”. Then, at the climax of Young’s “Rockin’ in the Free World” at a show in Toronto, Stephen Stills stumbles and falls over mid-song. Lying among the speakers at the front of the stage and still trying to play, he can’t get back to his feet and has to wave off a youthful helping hand. The indignity of it all.