Iolanthe, Gielgud Theatre, London

Now that we have established beyond all reasonable doubt that there are fairies in the Palace of Westminster, Gilbert and Sullivan's Iolanthe takes on a renewed vigour. Whether Gilbert knew quite what he was getting into with his tale of peers and peris, of moral tensions between Westminster and Fairyland, we cannot be sure.

But the idea of a half-fairy, Strephon, being sent to parliament to pass every bill he pleases because the Fairy Queen is furious with the upper house for their levity concerning his impending marriage to Phyllis (a ward in chancery) suddenly doesn't sound so far-fetched. And when Phyllis eventually learns that Strephon is half-fairy, is it not perfectly reasonable that she should ask him: "Which half?"

The pregnant pause, so to speak, between that question and its answer is but one instance of the knowingness that makes this second instalment in the Carl Rosa Company's short G & S season at the Gielgud almost as enjoyable as their Mikado. The trick once again is to trust the Savoyards absolutely and field a company who can play the style in that archly English manner, whose chorus of peers can advance on the audience and convincingly admonish them with the words: "Bow, bow, ye lower middle classes."

Gilbert and Sullivan knew their audience and so does director and designer Peter Mulloy. It's that delicate balance between charm and satire. There's a smashing moment when the Fairy Queen finally realises that she alone is without a partner and turning to the bluff Private Willis, sonorously played by Donald Maxwell, pops the question: "Would you like to be a fairy?" Maxwell's lips fleetingly purse and he turns to reveal a pair of tiny, sparkly, wings.

Bruce Graham and Barry Clark are a stalwart double act as the two Earls, Mountararat and Tolloller, and Steven Page as the Lord Chancellor gives vent to his torment at forever "giving agreeable girls away" in Gilbert's very brilliant "Nightmare Song" .

Last but not least – a collector's item. Maria Ewing as the Queen of the Fairies, decked out like Spiderwoman and sounding like a tremulous cross between Edith Evans and Margarita Pracatan , is certainly other worldly. But she can still deliver "Oh, foolish fay" like she's blissfully unaware of the double entendre.

To 16 February (0207-434 7590)