There's no way of avoiding a four-letter word here. The London Cuckolds is a "romp". A period piece, it's been billed as the No Sex Please, We're British of Restoration theatre, but it has none of the latter's manic energy. In this world of "gallants" and "nymphs", "pishes" and "forsooths", we follow the sexual fortunes of three husbands, three wives, a rake and his servant - and that's at least one husband-and- wife plot-line too many. We even have the play-within-a-play gimmick. This postmodern twist only adds to our sense of detachment. William Dudley designs a 17th-century proscenium theatre - with wings and balconies - that stands inside the proscenium stage of the Lyttelton. The actors leave the stage twice.
I wish Johnson had tried to make Ravenscroft as unfunny as possible, so we might see the horrors of loveless marriages, the fury of people interrupted when having sex, the dull anxieties of husbands, the desperate frustrations of wives, the terror of duels and the squalor of London streets. In farce, our pleasure exists in direct relation to the characters' suffering.
Watching this benign production, one's cheek-muscles strain with goodwill. Hard-working, a bit rude and going on too long: it's the National's equivalent to the best man's speech. The husbands are preposterous figures. The young wife from the country - an eye-catching Kelly Reilly - is an extraordinary simpleton. Caroline Quentin is confidently imperious, lusty and sarcastic as Arabella, and Alexander Hanson is handsome and smooth as the ex-lover Loveday, disguised as a bespectacled Scot with magical powers. But as the central character, the rake Ramble, the good-natured Ben Miles is neither serious, mad nor obsessed enough to drive this nonsense forward. It needs the horsepower of a young Donald Sinden. Despite the exhaustive humour the storydrags. When the denouement arrives it overstays its welcome. The city scrivener Dashwell (William Chubb) says, "I fear there's something more in this business," and one's heart sinks: no, not much more, please.
A first night is a piquant occasion for watching The Misanthrope, Moliere's comedy about the dangers of truth-telling. When the lights are down, we all nod along with Alceste in agreement that you have to speak the truth no matter what. When the lights come up, first-nighters mingle and dissemble in exactly the way Alceste's friend Philinte recommended.
This is the second production in Peter Hall's new rep season, and the pleasure of seeing familiar faces from recent Hall productions - Michael Pennington, David Yelland and Peter Bowles - doesn't compensate for the feeling that they've been miscast. Despite fulsome wigs, the hair is thinning on top of this Misanthrope. The cast look old enough to have children who could be appearing in their own productions. With this story it matters. With this level of uncompromising idealism, we don't want to think we're watching people with time-share options and early-retirement schemes looming into view.
It's partly that Pennington, who plays Alceste with a wry Home Counties weariness, should be playing Philinte. He hasn't the rage for Alceste, so Alceste never becomes a comic character. Insults don't spill out against his will. When he says "balderdash", the word itself is bigger than the emotion. Nor do we sense any sexual chemistry between Pennington and Elaine Paige's Celimene. I blame the hair-do and costume - the sartorial equivalent of a cold shower. Paige looks like a bar-girl dressed up to play a queen. There's more style in John Gunter's designs, in which a gilt frame hangs in front of the cobalt blue walls with a ladder leaning against one edge and half a snake slithering down from the top. Peter Bowles does his turn as the nobleman and aspiring poet Oronte, a foppish figure rrrrrolling his "r"s, pursing his lips and waving shirt cuffs large enough to cover a lampshade. He could do this in his sleep. Probably does. What's fascinating is the way Peter Hall gets far more laughs out of his superb Samuel Beckett production than he does out of Moliere. And you can't blame Ranjit Bolt, whose translation is never dull. In between the acts this Misanthrope uses TV-style theme music with hints of Mission: Impossible and the Bond movies. It gives it (briefly) an Art-like momentum. Now Matthew Warchus: there's someone who should direct Moliere.
On the way out of the song-and- dance show Kat and the Kings, which has transferred from the Tricycle to the West End, a South African TV crew asked what I thought. Kat and the Kings is set in the Fifties, in the controversial slum area of District Six in Cape Town, and tells the story of a group of young Cape coloureds setting up a band. I said it was great fun, had clever, inventive choreography, lovely singing, totally committed performances and bags of energy, and you could take the whole family. It didn't have much a story but that was probably an advantage when most musicals storylines are pretty crass. I can't imagine many foot-stomping, hip-wriggling, finger-clicking South Africans hopping on a plane to catch this one. But if you're near the West End, drop in.
'Cuckolds': Lyttelton, SE1 (0171 452 3000), to Jul; then touring. 'Misanthrope': Piccadilly, W1 (0171 360 1734), in rep. 'Kat': Vaudeville, WC2 (0171 836 9987).