IF YOU had asked me for an opinion of Terence Rattigan’s Man and Boy before this revival I might have quoted Jilly Cooper’s school report as she recently revealed it: “She has set herself an extremely low standard which she has failed to maintain.” Since the play has never had a serious showing since it faltered in London and flopped in New York over 40 years ago, I had only read the text — and reading suggested that it was contrived and a bit melodramatic.

Well, a considerable actor can make a great difference and, as his powerfully sardonic portrait of a bent financier shows, David Suchet is more than considerable. The play isn’t a masterpiece, but this marvellous actor left me agreeing with Bernard Levin, who back in 1963 stood out from the critical pack and praised Rattigan for his “dramatic cunning, narrative power and above all his restless imaginative curiosity about the springs of human activity”. Thanks to his theatrical alchemy, a potentially leaden play glistens with life.

It’s New York, 1934, and Roosevelt is rescuing America. Suchet plays the Romanian zillionaire Gregor Antonescu, whose business empire has survived the Depression but has been built on unsecured loans, dodgy deals and plunderings of the charitable foundation that he placed in his giddy, spoiled young wife’s name. Think of Robert Maxwell, and you have the man’s domineering hubris, as well as an ending I can’t reveal.

Anyway, Suchet’s Gregor appears with his sidekick — the excellent David Yelland, who is more than wintry enough to justify his name, which is Sven — in the Greenwich Village apartment of the son he long ago rejected as too soft, Ben Silverstone’s Basil. In a darkly comic scene he makes his last stand there, passing off the alienated yet adoring boy as his secret lover to the gay American magnate who can make or break him.

If you inspect the plot too closely, it seems faintly absurd: of interest mainly for what it reveals about Rattigan, who was at war with his own homosexuality and blamed it on the promiscuous father who had misused his mother and shown him too little love.

But at the Duchess you don’t inspect it too closely. You’re happy with the acting of all Maria Aitken’s cast, but you’re riveted by Suchet.

When Gregor says he can deal with hatred but “love is a commodity I can’t afford”, you should wince at the pseudo-psychology. But at the time you believe it, thanks to the wry urbanity that Suchet combines with deep cynicism, irresistible authority and a diabolic talent for manipulation as he creates a monster for 1934, 1963 — and today.

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