The body count and general level of gore in Shakespeare's histories and tragedies is notoriously high, but rarely has a production so taken this to heart: Jamie Lloyds gritty and brutal take on Macbeth indulges fully in the Bard's penchant for the horrible, with more the one rain of blood pouring from the ceiling of the Trafalgar's newly transformed main space. This, combined with Lloyd's post-apocalyptic setting, makes for a very begrimed production – most characters spend most of the play in a rather sorry state – but there's more here than just another young director's attempt to make Shakespeare relevant.

Although this production could not be more stuffed with contemporary references. Resembling ragged freedom fighters in caves more than noble warriors, the Scots wield machetes, axes and smoke canisters, mirroring modern rioters all over the world. The witches sport gas masks, their voices echoing (not always coherently), and there's plenty of combat gear. Apart from the visuals, the jagged sound effects and flickering lighting remind of modern shock horror movies, sending the audience into paroxysms of fear (there may have been an occasional shriek) at the abrupt scene changes.

In essence, there's really nothing wrong with any of this – Macbeth is a particularly demonic play, featuring a Scottish thane becoming king through assassination after being advised to by witches, and these elements all feel appropriate to the modern setting. However, they do have a tendency to obscure and confound: by the interval, I was feeling more disappointed by Lloyd's concept than engaged. There's an overwhelming feeling here of trying to make Shakespeare cool, modern and relevant, but some of the story and themes go wanting.

For example, making McAvoy's Macbeth the Gerard-Butler-esque freedom fighter is all well and good, but how can a man we first met blood-caked be so afraid of murdering a king? And what is a king in this post-apocalyptic world – and why is lineage so important? It doesn't gel. There's also some rather over-directed moments – the intimation that Lady Macbeth's desire for power is in response to losing a child (adding real poignancy to "I have given suck...") isn't new, but trying to shoehorn in a hand to the belly and a shake of the head (when there are no lines to go with it the first time) just feels odd. And the decision to have a small contingent of the audience behind the action is also strange, with some scenes being missed by most of the audience because of it.

But there is a greater theme at work here, and it really comes to the fore during the second half. Lloyd takes a strong anti-violence stance with his nuanced direction of Jamie Ballard's Macduff – no longer the hero returning to defeat the tyrant, Macduff is made just as violent and as dirty as the tyrant he's trying to defeat. He looks just as mad next to the gun-toting Malcolm as Macbeth does – and McAvoy's portrayal becomes sublime as he goes from arrogance to acceptance of his fate. All of this cool post-apocalyptic window-dressing becomes a metaphor: a stance against modern violence and the excesses of war, and finally making it relevant to the piece, not just the audience.

It takes it time then, this Macbeth, but it proves much more than the sum of its parts by the curtain. McAvoy puts in a confident and assured performance, and is a pleasure to watch – and by the looks of the audience, is attracting one for his ability as well as his looks (which is probably for the best – he spends most of the piece rather bedraggled). There are plenty of flaws here, including some very basic ones (the dull thud of plastic sword against plastic axe being just one), but by the end you may well be blown away – I certainly was.

Macbeth, at Trafalgar StudiosChris Hislop reviews Macbeth starting James McAvoy at Trafalgar Studios.4