Few 80s cultural artefacts have accrued the same level of enduring audience goodwill as the time-travelling adventures of the sweet-natured California rockers Bill S Preston Esq and Ted “Theodore” Logan. And it’s fair to say that this goodwill is required to do a fair amount of heavy lifting with this endearing but shambolic sequel.

The film rejoins Bill (Alex Winter) and Ted (Keanu Reeves) as middle-aged dads who aren’t so much has-beens as never-beens. Tasked with writing the song that will save civilisation, they have so far failed, and are reduced to prog rock noodling on theramins and bagpipes. And now the stakes are raised. Another, somewhat exasperated visitor from the future (Kristen Schaal) arrives to urge the pair to get their act together or not only will reality itself cease to exist, their marriages will crumble. Faced with this heinous turn of events, Bill and Ted do what they always do – tool around time in a souped-up phone box, occasionally stumbling upon answers. Meanwhile, their daughters are zipping through history in order to assemble the ultimate supergroup (Mozart, Hendrix, Louis Armstrong), an excess of talent given the godawful Hooked on Classics-style abomination they end up playing.

Scripted by the original creators of the series, Chris Matheson and Ed Solomon, the film makes a virtue of its anachronism, both in the now creaky surf vernacular and in the complete absence of cynicism – the film’s saving grace. This slapdash movie, with its big-hearted, puppyish positivity, might not save the world but it will surely lift the spirits.