For that was the era of the cult of the young, brilliantly captured in a moment in Summer in the City when one character bemoans her persistent lack of success and fame: “I’m not getting any younger. I’m nearly 21.”

It’s one of several lines designed to provide the audience with a knowing chuckle. Here’s another. An American asks a young woman who wants to go to art college, but can’t afford to, whether you have to pay tuition fees in Britain. She’s horrified at the idea: “Then no one could afford to go to college.” The same American thinks rock and roll is a passing fad: “Are the Rolling Stones going to be rocking and rolling in their seventies?” Of course not; what an absurd idea.

The energetic and accomplished cast sing, and dance, and act, and charm their way through the evening. For me the standout is the Four I’s proprietor Hetty (Helen Goldwyn), a Jewish matriarch based, apparently, on John Plews’s mother, who keeps dropping Yiddish words into the conversation, at one point conflating brown sugar with meshugge (which means mad.)

Liverpudlian Bobby (Harry Curley) brings his guitar on stage for simple and delightful renderings of ‘Ferry Cross the Mersey” and “I’m a Believer”. The three young women, Joanna (Eliza Shea), Cassie (Candis Butler-Jones) and Vera (Elizabeth Walker), tug our heartstrings with their naïve ambition and belt out their songs with tuneful gusto – the show opens with Hetty singing “Downtown”. The American, Sam (Connor Arnold), all slicked down hair and brash ambition, reminds us that male chauvinism was far from dead in the sixties.

But in the end, of course, all is well. “I do love a happy ending. Mazel tov” says Hetty. It could be John and Katie Plews, as they take leave of their theatre and hand over to their current theatre manager Annlouise Butt and her partner Isaac.