First Night: Never So Good, National Theatre, London

Macmillan, from boy to man, portrays the inside Tory

Among the things you might not expect to see at the opening night of a new Howard Brenton play, Jeffrey Archer sitting proudly in the fourth row comes pretty high up on the list.

There must be something in the water. First David Mamet declared himself through with being a "brain-dead liberal" and now Brenton, the one-time self-professed Marxist and celebrated left-wing satirist has gone and written an elegiac and profoundly human portrait of the Conservative Prime Minister, Harold Macmillan.

Ever since Mary Whitehouse tried to ban hisRomans In Britain, Brenton has wielded the power to shock. And while he is back in the political arena after his last two religiously-minded works, Paul and In Extremis , on this occasion his satirical sword remains, surprisingly, in its sheath. From the very first genial line, "I always had a lot of trouble with my teeth", Brenton shows us Macmillan the man.

We see him from his earliest days, playing the Eton wall game, crushed by a domineering mother and a flagrantly unfaithful wife (played with limp-wristed grace by Anna Chancellor) and fighting in the First World War, up to his crowning as "Supermac", the Tory leader who told Britons they had "never had it so good" and his eventual resignation in the seedy aftermath of the Profumo scandal.

He is, in Brenton's likeable, amusing version, a sympathetic mix of the ridiculous and the tragic.

Howard Davies' direction is suitably epic, stylishly rising to the challenge of staging some 40 years of history, encompassing two World Wars, the crumbling of the Empire, the Suez crisis and the dawn of the swinging Sixties. The changing decades are rung in with dance – a spine-tingling waltz towards war, a jubilant victory lindy-hop, and a shimmy into the 1960s – and there are magnificent setpieces, including a moving Somme sequence.

As Macmillan, an unrecognisable Jeremy Irons perfectly captures a man who is fatally out of step with his time. His stuffy drawl through his soup-strainer moustache is spot on, as is his body language; his little jig when he finally gets one over on his wife's lover Boothby is a delight.

He is well supported by Pip Carter as the youthful (but still absurdly old before his time) Macmillan who dogs him mentally throughout his life. In an excellent ensemble cast, Ian McNeice's corpulent Churchill provides nice comic relief while Robert Glenister's Boothby makes a horribly convincing journey from slick rake to bloated old duffer.

When asked by a journalist what causes the downfall of a government, Macmillan famously waffled, "Events, dear boy, events". Or, in today's political vernacular, "stuff happens". The beauty of Brenton's play lies in such modern parallels, the ever-repeating cycle of "events" at the chaotic epicentre of government: the sex scandals, the private Catholicism, the shady dealings of war, the messy entrails of an economy in meltdown.

And, at its heart, the less than charismatic man next door, seizing the reins of power from his glamorous predecessor after an agonising wait only to see his premiership unravelling before his very eyes.