The Royal Hunt of the Sun, NT Olivier, London

After enduring about an hour of Trevor Nunn's excruciatingly passé revival of this conquistador saga, penned by Peter Shaffer in 1964, one punter in front of me turned to his companion with a look of incredulity. He then had to pinch his nose to stifle a fit of appalled giggles, so I guess he wasn't officially contributing to the soundtrack of equine whinnies that was meant to be souping up the mime sequences.

Picture, if you will, much pointless banner-swirling, then pretend horse-riding followed by lots of vague clambering over imaginary logs in the Peruvian jungle amidst lashings of dry ice. It is as if decades of more sophisticated physical theatre have been obliterated and we are back at square one. On top of that, Shaffer's most famously challenging stage direction - "They cross the Andes" - merely inspires what looks like laundry day: a couple of white sheets yanked up on ropes to suggest the awesome peaks.

Meanwhile, the native tribes in the lush valleys beyond seem to be living in a kind of giant Copacabana cocktail, a permanent touristic sunset of orange and crimson (design by Anthony Ward with lighting by Hugh Vanstone). Anthropologically, it all looks embarrassingly unconvincing, like Inca: The Musical, especially when everyone starts parading round with vast gold-sprayed vases and platters which clearly weigh little more than tubs of popcorn. This may be a relatively low-budget production (part of the Travelex £10 Season) but the lack of creativity is dire.

To be fair, this history play about imperialism and clashing belief systems is not without interest or relevance. It tells the story of the ageing, fame-seeking general Francisco Pizarro (a grizzled Alun Armstrong) and his 1532 invasion of Peru with rough troops and zealous priests. They claim their mission is to bring progressive Christian values to the heathen, but really they are greedy gold-hunters who ruin the great Inca civilisation.

They wonder at this newfound kingdom, at its epic roads, its city squares grander than any in Europe, and its rural populace who seem to live in a state of serene egalitarian bliss. But when they finally track down the deified sovereign and proclaimed descendant of the Sun God - Paterson Joseph's splendidly regal Atahuallpa - they massacre his welcoming retinue, imprison him and melt down the country's treasures.

Stuff happens. Eventually, though, the honour-scorning and atheistical Pizarro - having befriended his captive and then broken his word - suffers pangs of conscience and is mentally destroyed. He ends up desperately wanting to share Atahuallpa's deep faith in his own immortality and in the myth that, after being brutally executed, he will rise again from the dead.

At his best, Shaffer offers passages of vividly descriptive prose-poetry, philosophising and religious satire; but the big ideas are often spelled out heavy-handedly. As for the cast, half are overacting while others are underpowered. Armstrong needs more time to find deeper despair in Pizarro. Nevertheless, the evening becomes increasingly gripping. There are strong supporting performances from Darrell D'Silva as Pizarro's frustrated right-hand man, and Paul Ritter is a horribly funny, morally-twisted friar. Also, thank heavens, Joseph is wonderfully canny, warm and vibrant as Atahuallpa. Theatrically, if not politically, he nearly saves the day.

k.bassett@independent.co.uk

To 10 June, 020 7452 3000