Plague Over England, Duchess Theatre, LondonOn the Waterfront, Theatre Royal, London

Nicholas de Jongh all but silences critics as he turns a sharp, funny, playwright's pen on bigotry

You have to admire Nicholas de Jongh, emerging from the safety of his first-night seat to take the limelight as the author of a West End play. The standard riposte to a disappointing review is, "If you know so much about it, let's see you do better". As theatre critic of the Evening Standard for 18 years, De Jongh rises to that challenge. He should, after all, know how to squeeze a tear or raise a laugh.

There are jokes aplenty in Plague Over England, for De Jongh delights in the often laughable values of politics, the theatre and newspapers, and in one-liners, original or recycled with affection. The play hinges on the conviction of the recently knighted actor John Gielgud on 21 October 1953 for importuning in a public lavatory. He has been set up by "the Pretty Police", in an England where homosexual acts will be illegal for another 12 years and in a political climate that harnesses the voter power of moral indignation.

As Gielgud, Michael Feast catches many of the man's familiar and well-loved mannerisms – the camel-haughty turn of the head, the glissando vowels (" Much the best wa-a-a-ay"). And when he is cornered by the attractive young PC, his brittle facade vanishes in an instant to reveal a cowering mouse, in one of the few moments when the pain, loneliness and injustice of his state eclipses the verbal slapstick. Around this feeble victim swirl characters real (Celia Imrie brisk and indulgent as Sybil Thorndike), invented or conflated. In the shadows, young men fall in and out of love, and will go on to march with Gay Pride as the play leaps abruptly to a more enlightened age, via a dull, wibbly-wobbly fantasy sequence. But the implication that everything is all right now is oddly parochial – homosexuality is still illegal in 80 countries, and many victims of persecution flee, scared and scarred, to Britain.

So, does De Jongh do it better? Well, Plague Over England is episodic, falls back on Tunbridge Wells for an easy laugh and is heavily weighted one way, which does not make for challenging drama. And yet, it is a pleasing evening. The acting is vigorous, and for the first time in 40 years at the theatre I didn't have to queue for the Ladies.

Steven Berkoff revisits another landmark in performance history with his production of On the Waterfront, Budd Schulberg's searing exposé of corruption in the New York docks. Anyone expecting to see a replica of the Oscar-winning film that confirmed Marlon Brando as the most exciting actor of his generation will come away with an entirely different experience. For Berkoff, with characteristic inventiveness and clarity, gives us his own vision of the menaced lives of the longshoremen who dodge for survival between the twin dangers of the work they desperately need and the murderous gangsters who dish out jobs in exchange for backhanders.

On a bare stage, darkly threatening places are created solely by Mike Robertson's remarkable lighting and the physical theatre of Berkoff's men – and Berkoff himself, as head hood Johnny Friendly, creepily avuncular with a prosperous paunch but always on the edge of violence. The play opens with the mob glad-handing in their enormous, high-end overcoats, shoulders hunched, elbows cocked, secrets masked by tilted hats, abnormally solid, like the thick-limbed figures of Fernand Léger. These massive slow-motion beasts roll to and fro, prowling and sizing up the dockers who flail against their wretched lot like injured prey.

To a soundtrack of Fifties jazz and chart hits and Mark Glentworth's thrilling live score, the longshoremen's rebellion gathers momentum, with Terry Malloy as its reluctant leader. Simon Merrells as once-promising boxer Malloy reveals painfully the thickened speech and dimmed brain of the prize fighter, whose flattened social conscience is revived by love.

There is light amid the gloom – a pigeon loft stacked with cooing, ruffling actors, docker Runty Nolan's relish at the prospect of raiding a whisky consignment: "You see the beauty of a little man in a big coat." It all adds up to a rare treat. Precious cargo indeed.

'Plague over England (020-7850 8720) to 19 Mar; 'On the Waterfront' (0845 481 1870 to 25 Apr

Kate Bassett is away