BD. Before Dorothy. That’s the starting-point for Stephen Schwartz and Winnie Holzman’s smart, winning musical Wicked. Actually, the irritating little girl in the blue gingham dress blows in from Kansas roughly two-thirds of the way through Act 2. But by then things have come to a pretty pass in the Land of Oz. The Wonderful Wizard is not all he seems, Elphaba – later the Wicked Witch of the West – is clearly far from wicked, just as Galinda – later Glinda the Good – is, well, far from good. Popular, yes. Good, no. Who says politics isn’t rooted in fairy-tales?

Wicked has been an unprecedented smash on Broadway for more than two years now, breaking all previous box office records at the Gershwin Theatre. Whether it can replicate that success in London, where it opens in September, remains to be seen. Up until now London has proved something of a jinx for its composer and lyricist, Stephen Schwartz. Only Godspell really made an impression; even Pippin (probably his finest work before Wicked and a Tony Award-winning legend on Broadway) faded fast; and not even Trevor Nunn could salvage The Baker’s Wife (a terrific score in search of a workable show). So I for one am willing Wicked to succeed. It’s a smashing evening in the theatre (I speak as one who’s seen it three times on Broadway) and this is a corker of a cast album.

Style-wise Schwartz is still very much a child of the 1970s and ’80s. There’s a touch of the die-hard hippy about him. Beautiful ballads like ‘I’m not that girl’ and the super-touching pay-off duet ‘For good’ have the fragrant whiff of classy retro pop about them. Still, the stylistic remit is far-reaching. There’s a terrifically clever and exciting set-up sequence – big and operatic – where Schwartz and Holzman ingeniously lay out their stall for the evening. There’s a peach of a take-home number, ‘Popular’, where Galinda (the irresistible Kristin Chenoweth) propositions Elphaba with a makeover: ‘Don’t be offended by my frank analysis, think of it as personality dialysis’ (how’s that for a smart line). And there’s the ear- and eye-popping Act 1 clincher ‘Defying gravity’ where laser-voiced Idina Menzel (who’s reprising her Tony Award-winning Elphaba in London) rides William David Brohn’s iridescent, keyboard-festooned orchestrations (what a sensational piece of work) into premature immortality.

To quote from another song in the show: ‘I couldn’t be happier.’