Follies, Royal Festival Hall, London

You could pitch the proverbial row of pink tents along the full length of Old Compton Street and not end up with anything half as camp as Stephen Sondheim's Follies.

Mid-1970s and a gang of superannuated, 50-something ex-chorines are meeting up for a first and last reunion before their Broadway Theatre is demolished to make way for a parking lot. Well, that's what happens in a nation that puts cars before cabaret.

The upshot of this scenario is there is no end of good roles for 50-something ex-chorines, oozing with talent, technique and excess time on their hands, to strut on stage and do cameos. The scenario also gives Sondheim the chance to write no end of pastiches of Thirties numbers. Come back, Ziegfeld, all is forgiven.

But what about the story? Well, you have to wade through an hour of exposition and pasticherie before you get to even the faintest glimmerings of some narrative. But don't get your hopes up: thirty years ago Ben loved Sally but married Phyllis, Buddy married Sally but she still loves Ben and Phyllis is just plain angry. That's it. What's strange is that, in a production that boasts that it is "fully staged" (as indeed it is), Sondheim and his librettist, James Goldman, never bothered to stage it in the first place. The songs bang on regardless of storyline – all under the excuse that it's a semi-musical reunion of semi-musical performers – and the chunks of dialogue are patchy and sophomoric in their insights, not helped by the piano bar tinkling under most of them.

But staged it is – Paul Farnsworth's phenomenal, shabby, once-grand theatre interior dominates the RFH stage and half the auditorium. The young chorines parade in an ever changing array of costumes and I'll forgive the anachronistic hip-high cut of the leotards. The band pumps out a glorious sound and the only disappointment of Paul Kerryson's production is the singing is often underpowered. American Equity is crawling with aged divas who can shatter crystal at two hundred paces without breaking sweat. Sadly, Britain is not so blessed and they are overwhelmed by orchestration.

Yet, in spite of all that and of some clunky lighting cues, when Sondheim hits the big torch numbers – "Too Many Mornings" and "Losing My Mind" – a thrill runs up the back of your neck and it all seems to make sense.