It is certainly sing-along time with a difference when the couple let out a defiant chorus of "Portaloo, Wouldn't escape if they told us to. Portaloo, Oh, oh, oh..."
All right, only kidding. In fact, Abba's Eurovision triumph is one of the very few hits they don't manage to shoehorn into the show. By the standards, though, of those K-Tel compilation West End musicals, Catherine Johnson's book does a nifty integration job with an original plot involving a young girl on the verge of marriage and her relationship with her mother when she discovers that any one of three men could have fathered her.
The real drama, however, is less between the characters on stage than between the audience of fans and the music. A defiantly camp note is struck from the opening announcement: "We'd like to warn people of a nervous disposition that platform boots and white Lycra will be worn in this production."
The show proceeds as though the fans have generously donated the songs to it for the evening and will sit there ready to exult at each deliriously outrageous way the makers engineer the next opportunity for a ditty.
It's certainly handy that the prospective bride's mother (the excellent Siobhan McCarthy) used to front a Seventies rock band and that she has invited her old backing singers (Louise Plowright, a leggy comic broad, and Jenny Galloway, who plays a very funny mini-mountain of a Rosie) to the wedding on the Greek island where she owns a taverna.
No excuse, then, for them not to break into an "impromptu" rendition of "Dancing Queen", with hairdryers, vibrators and roll-on deodorants as microphones, that is designed to bring out the dancing queen in the straightest soul.
Indeed, even the most avid collectors of kitsch cues for a song might find themselves amazed as the two friends comfort the mother with mock- solemn solace of "Chiquitita", or as one of the possible fathers unwraps Alan Partridge's Pringle sweater from Knowing Me, Knowing You and improbably warns the bride-to-be of the pains of divorce.
The island setting allows for camp underwater dream sequences of a Jacques Cousteau-meets-Esther Wil-liams variety. But there are also moments of heartfelt feeling as when McCarthy helps the daughter dress for her nuptials and sings, in pulsing voice, "Slipping Through My Fingers", here a lovely lament for the way one's children continually elude one until they finally leave.
Phyllida Lloyd's handsome production generates a terrific mood of airborne silliness and the songs, a curious mix of the buoyant and the haunting, are genuine golden oldies. Abba is pop's pithiest palindrome and, whichever way you read it, Mamma Mia! looks like being a hit.