Henry V, Olivier, National Theatre, London ****

A youngish head of state commits his armed forces to the risky invasion of a foreign power. The grounds for this attack are morally and legally dubious and the justifications scraped together are strained. He scores a victory, but not before his vaunted Christian morals and accountability to the common man have been exposed as wanting. On the one hand, he's viewed as a courageous hero; on the other, he's seen as a self-interested myth-maker, eager for a purple passage in the history books.

You don't need to be Clare Short to feel that you have heard this one before. And certainly a trip to the National Theatre to see Nicholas Hytner's searingly sceptical modern-dress production of Henry V – a play which (from at least one of its clashing perspectives) tells much the same story – would be something of a busman's holiday for Tony Blair. But Hytner does not force the analogy – Rory Bremner has not been cast in the title role. But the mood of the times has surely prompted him to stress and embellish those aspects of Shakespeare's deeply equivocal patriotic drama that are most uneasy and questioning about the morality of war.

The Chorus in this version is no booming, foursquare male jingoist, but a hero-worshipping PA (Penny Downie) whose deluded raptures about the king and his campaign are sometimes allowed to be rudely undercut by grimmer reality. Right from the start, the production's anti-heroic stance makes itself felt in the unlovely boardroom scene where a raffish, self-serving Archbishop of Canterbury bores for Britain on the subject of the convoluted legalisms that could authorise the invasion of France.

Refrigerated and severe, liable to career in an instant from eerie restraint to cold fury, Adrian Lester's powerful, charismatic Henry is evidently overcompensating for his reckless youth in a determined and sustained display of humourless righteousness.

He's the kind of person who won't be seen to move without the guarantee that God is on his side, while at the same time not being overly fussy about the quality of the assurance.

The vivid, well-staged military scenes – where many of Henry's speeches are delivered to camera for the propaganda war and later watched on television, with French subtitles, by the enemy – sometimes show a more sympathetically human and uncertain monarch. But his ruthlessness is also chillingly conveyed in the scene where, in retaliation for a counter attack, the English king orders the killing of French prisoners. In Hytner's account, this so sickens his soldiers that most of them refuse to comply and it's left to one maniac zealot to carry out what is a war crime. The stink of sanctimony pollutes the celebration of victory here as we watch a sentimentally edited documentary about the war, screened with a rap soundtrack thanking God for having the wisdom to back the right army.

What Henry lost as a human being when he became king is fleetingly and nostalgically glimpsed in a home video of him as a rasta-locked Prince Hal down at the boozer in an uproarious session with Falstaff and gang. His idea of fun in this play has shrivelled to playing sneaky, calculated tricks on people, while his thickly laid-on charm and disingenuous pose of simplicity in the wooing scene signally fail to melt the French princess (a delightful Felicité du Jeu). She reacts with stiff, stricken distaste, clearly regarding this heavy artillery chat-up as just the continuation of the rape of her country by more courtly and cringe-making means.

At the end, the gushing Chorus (more sombre and unsure now) informs us that peace was painfully short-lived. In the next reign, France was lost and civil war erupted. The last-minute look into the future lends a troubling irony to the awkward photographic tableau of cross-Channel unity assembled upstage. A sense of the swift perishability of the fruits of war is another reason why this single-minded and challenging version of Henry V might not make such a relaxing evening for the Prime Minister.

To 20 August (020-7452 3000), part of the Travelex season at the National Theatre