WHERE Christmas adaptations of Dickens are concerned, Scrooge got it right: Humbug. A big marketing point for both Oliver! and A Christmas Carol is that these works become ever more relevant with the increase of London's homeless: as though people plunging into a night's seasonal escapism can also congratulate themselves on exercising their social conscience. Bah! I did not spot any of the dinner-suited throng elbowing their way into the Palladium or the Barbican pausing to buy a Big Issue or spa re a glance for the Underground beggars.

Nor has the return to Victorian street life made any impression on the shows themselves. Juvenile Bosnian pick-pockets may be roaming the West End, but Fagin's gang are still the pack of lovable urchins from Lionel Bart's Cockney never-never land. The news that Sam Mendes was directing this revival of Oliver! aroused the idea that the show could change with the times. A false hope. For good or bad, Olivier! is what it is: a capable melodrama with one good role and a set of thumpingly memorable tunes that serve to neutralise the cruelties of the story and stop you asking awkward questions - eg, if Mr Brownlow is such a kind-hearted old party why did his pregnant daughter have to flee to the workhouse during a thunderstorm?

Mendes's production offers everything you could want in the way of efficient stage management. The juvenile chorus is winning and well-drilled; picturesque street scenes, with tumblers, balloon sellers and lovely toy-theatre machines take shape and vanish in the twinkling of an eye. Anthony Ward's sets are no match for the mechanised marvels of Sean Kenny's 1960 design, but - with their Nash Terrace perspectives and murky caverns of crumbling brickwork and subterranean plumbing - they convey the essential Dickensian contrast between escape and imprisonment.

Perfectly organised, the narrative speeds along like a train, seldom stopping to let you admire the view. There are two exceptions: Bumble's number "Boy for Sale" (sung, against character, with great poignancy by James Saxon) and the canon of London street cries which magically transforms the urban drama into a pastoral. Otherwise the company steams ahead, leaving you feeling dramatically short-changed in spite of the emphatically prolonged numbers.

There is nothing wrong with the performances. Miles Anderson intensifies the menace of Bill Sykes by letting him relax and grin. Gregory Bradley's Oliver makes a gutsy transition from pathetic submission to knocking the stuffing out of Noah Claypole. Sally Dexter is a magnificent Nancy, leaving you in no doubt about her trade as she mounts her customers in "Oom-pah-pah". But there are few surprises; even Jonathan Pryce's Fagin limits his invention to a few conjuring tricks and children's party dances. He is, however, the best reason for seeing the show. Swift and graceful as an adder, delicate as well as brutal, and disdaining Hebraic impersonation, he is another eternal survivor like the Engineer in Miss Saigon and brings the sense of cosmopolitan experience into the thieves' kitchen. Oliver's story is only one passing episode in his career.

The best thing about John Mortimer's adaptation of A Christmas Carol is Nigel Hess's beautiful score. This is the first version of the story I have seen that takes the natural course of treating it as a carol service. Elaborately arranged, the old songs also merge into atmospheric accompaniment, and replace the need for inventing dialogue. Mortimer often relies on the trick of putting third-person narrative into the characters' mouths, which, though chorically effective, underlines the facetious tone ofIan Judge's production.

There are some pretty English heritage settings (John Gunter) and deft crowd scenes, (notably the Fezziwigs' festive thrash); and the three ghosts culminate in a genuinely spectral 18ft ghoul with a mechanised index finger. But there is no hiding the fatal lack of belief in the story. Clive Francis's Scrooge from the start is a comic ogre, bantering with Marley's ghost, and finally shedding a good 20 years with his change of heart.

Next Thursday The Man of Mode, Etherege's supposed portrait of the Earl of Rochester, opens at the Royal Court. In the meanwhile we have Rochester in person, in Stephen Jeffreys' The Libertine, telling Etherege he could have written it himself. So why didn't he? "I was too busy living it," he says. "I am the age. I don't want to be its chronicler."

That is the closest Jeffreys comes to saying what this piece is about. As a dramatic character, Rochester is instant box office: man of action, rake, crony of royalty, devastating wit, self-destructive genius, and, to cap it all, a lover of the theatre. The question is, what do you select from this to make a play? Jeffreys opts for a chronicle of his hero's marital and extra-marital sex life, interwoven with theatrical and coffee-house intrigue. Given the author's proven skills in pastiche and anachronism, this yields a fluent and arresting narrative, particularly in the scenes with Charles II (poised between chumminess and alarming returns to protocol in Tim Potter's excellent performance), which take advantage of the most scabrously dazzling verses ever swept under the carpet by English scholarship.

The effect is to turn Roches-ter's life into the kind of moral fable he would have despised. Here is a man dedicated to the pursuit of pleasure who is manifestly having a rotten time. Failing to achieve an orgasm on the one occasion he is shown coupling,forever crawling back to his wife for another paroxysm of maudlin guilt, failing equally to stage his naughty drama Sodom for the King or to reap the reward from his theatrical protegee (Katrina Levon), he winds up as a palsied wreck, retching his guts out as he empties his last bottle of wine on the carpet.

A parallel has been drawn between Jeffreys' Rochester and Osborne's Jimmy Porter in Look Back in Anger . When Jimmy first appeared, sceptics asked what he had to complain about. It might seem equally fatuous to ask this about Rochester, except that Jeffreys does try to answer it. Rochester sank into nihilism, it seems, because the mediocre Charles failed to ignite into England's Sun King, the suggestion being that if an autocratic monarchy had followed the Commonwealth, Rochester would have spent his life as a blameless husband churning out panegyrics for his royal patron. Such is the nonsense into which the play runs by excluding Roch-ester the philosopher, who understood the word "libertine" in its French sense, denoting intel-lectual as well as sexual freedom.

At least he gets a fine, gratingly intransigent performance from David Westhead; and Max Stafford-Clark's production projects a world in which night brawls, a ladies' chorus in praise of "Signor Dildo", and austerely concentrated debate on the art of theatre are equally at home.

In Garrick and Colman's The Clandestine Marriage the hard-edged satirical figures of Rochester's time have lost their sting. This is not necessarily a loss. If he had appeared a century earlier, for instance, Mr Sterling would have been a miser and nothing else; in Garrick's hands he is also warm-hearted and an obsessive sucker for fashionable "improvements" to his estate. Much more interesting; and brought to boomingly sympathetic life by Christopher Benjamin. The improvements themselves (I remember anal fresco cocktail cabinet and electrified birdsong in a previous version) are beyond the bounds of Nigel Hawthorne's production which makes do with actors impersonating topiary hedges. But these are enough to get the joke across, and also to show Lord Ogleby - the lecherous old wreck gorgeously played by Hawthorne - overcoming his distaste for pastoral diversions and skulling round the stage in a boat, thus prefiguring his own change of heart. It is a sumptuously dressed, inventive, gene rous show in which Susan Engel and Deborah Findlay, as a dragonish aunt and her brattish niece, deliver the funniest double act to be seen in London.

`Oliver!': Palladium, 071-494 5020. `Christmas Carol': Barbican, 071-638 8891. `Libertine': Royal Court, 071-730 1745. `Clandestine Marriage': Queen's, 071-494 5040.