HELLO, good morning and welcome. Welcome to Michael Grandage’s absorbing production of a play that last night did two unexpected things. It showed David Frost shedding his genial, tabby-cat image, finding his claws, and becoming as tigerish as any Humphrys or Paxman. And it managed to win a little sympathy for his unlovable prey, Richard Nixon.

The author is Peter Morgan, justly admired for The Deal, the television drama he wrote about the Blair-Brown pact. Frost/Nixon, his first work for the stage, is also a mix of reportage and informed speculation, derived both from the record and from interviews with those in the know: our John Birt, the American journalist James Reston, and others who in the 1970s helped to set up Frost’s interview with the disgraced ex-President.

As often with docudrama, you’re not sure how far Frost/Nixon is to be trusted, but there can surely be no doubting the authenticity and power of its climax. Nixon seems effortlessly in command of Frost’s many taping sessions, but the very last involves Watergate and Tricky Dickie’s refusal to acknowledge the degree of his complicity in its cover-up. And that dogged matador, David Frost, has evidence that, as Reston puts it, reduces Nixon into a bull that suddenly realises it has lost the fight and “the will to live”.

With Michael Sheen finding serious steel behind the laid-back Frost exterior, and Frank Langella suddenly transformed into his mottled, sweating victim, this more than justifies the longish build-up. Can Frost raise enough money to lure the financially needy Nixon before the cameras? Can he keep onside his sceptical American advisers, Elliot Cowan’s fiercely principled Reston prime among them? Morgan and Grandage could have trimmed the piece a bit, but they keep the tension surprisingly high throughout what might well have seemed an old story and even older news.

Is there a lasting point to it? Only that patience, determination, careful research, skilful interrogation and a bit of luck may lay bare a carefully concealed truth. But what gives the evening its frisson is partly the sense of watching history being made, and also the not-wholly-different characters of the principals. The careers of both Frost and Nixon are becalmed, the latter in a political Antarctica. Both hope the interviews will revivify them. And each comes from an unprivileged background which, it’s suggested, has given him a desperation to succeed.

At any rate, that is what Langella’s hoarse-voiced Nixon claims in a phone call to Frost’s hotel that’s packed with self-pity, paranoia and tipsy fury at a world of “snobs”. All along his has been a fine performance: given to comical shows of sentimentality, yet tough, canny, controlled. Sheen, too, has done much more than ape Frost’s weirdly looping vowels and clubby assurance. But now we see the insecurity, the inner vulnerability the two men share and hope not to show. Factual, fictional, it makes for riveting drama.

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