The theory of evolution went on trial in Tennessee in 1925 with the arrest of a young science teacher for telling kids about Charles Darwin. When Jerome Lawrence and Robert E Lee wrote a play about the case 30 years later, it was seen as a metaphor for McCarthyism. Alarmingly, with creationism back in full cry in the US, it needs to be taken literally again.

We’re not in the States, though. Inherit the Wind is meant to be director Trevor Nunn’s contribution to this year’s Darwin anniversaries (200 years since his birth, 150 since the publication of Origin of the Species), but it’s much less relevant over here than in America. His caution in falling back on this occasionally clunking courtroom drama looks sadly like another example of the Old Vic’s obsession with all things American under Kevin Spacey’s helm.

Spacey himself plays defence lawyer Henry Drummond, modelled on the real-life legal magician Clarence Darrow. He enters at the end of the first act, white-haired and stooping, with a coffin-pallor, and the transformation is exciting: for a moment it seems as if the Old Vic’s biggest crowd-puller is going to break out of the samey mode that has made his performances so familiar after five years.

That hope is quickly dashed. This Spacey may have visually aged 20 years, but his delivery relies on the usual combination of deadpan sarcasm, theatrical pauses and shouty fury. The real Darrow was described as “America’s greatest one-man stage draw”, but we don’t see it here. When a previously God-fearing crowd comes round to Drummond's side in the third act, it just seems contrived.

As opposite number Matthew Harrison Brady (based on the presidential candidate William Jennings Bryan), David Troughton gives the real star turn. With a rubber face, an expressive sniff and fidgety shoulders that seem to operate independently of the rest of him, he’s a lumbering bear of a political demagogue who shrewdly modifies his delivery in the courtroom and ends up as a blubbering child when reduced to ridicule.

Among the rest of the huge cast – 26 speaking actors, 34 non-speaking townsfolk and a real-life monkey – Sam Phillips is by turns respectful and defiant as the heretic Bertram Cates and Sonya Cassidy is powerful as his conflicted sweetheart Rachel. Mark Dexter provides nasal wisecracks as the cynical journalist EK Hornbeck, based on the real-life HL Mencken.

But with everyone decked out in sepia, on a courtroom-based set by Rob Howell that isn’t as inventive as it would like to be, it’s visually underwhelming. There are moments in the enormous crowd scenes when the piece feels like it’s about to become a big Trevor Nunn musical. But even if it did, you get the impression the tempo would never rise about the townsfolk’s “Amazing Grace” dirges.

A well-meaning challenge to religious mania, the production doesn’t deserve to go the way that Nunn’s previous breeze-related venture, Gone With the Wind, did last year. But it’s more a zephyr than a cyclone.