Six Characters In Search Of An Author, Gielgud Theatre, London<br />War Horse, National Theatre: Olivier, London

Rupert Goold is a name that will give any project legs at the moment. The award-winning 36-year-old director has a production of No Man's Land, starring Michael Gambon, and the I'd Do Anything-promoted extravaganza of Oliver! lined up for the West End this autumn, and a major production of King Lear with Pete Postlethwaite opening in Liverpool in the same crammed season.

All the same, you have to admire the steady nerve and the vision of the producers who have brought his and Ben Power's multimedia adaptation of the Pirandello classic, Six Characters in Search of an Author, from Chichester's Minerva Studio to the Gielgud Theatre on Shaftesbury Avenue. Not since Rufus Norris's brilliant version of Cabaret two years ago has theatreland's commercial sector been treated to such an exhilarating booster jab of radical reinvention and rampant imagination.

Everyone involved in the transfer merits special praise because they have not just preserved the weird, mind-bending intellectual integrity of this fiercely fresh take on the play. With enhanced production values for the live and pre-recorded filmic elements, the show has now expertly heightened the emotional effect of the constant disturbing clashes between different levels of reality and modes of existence.

In this version, the six characters – who have been abandoned by their author and seek redress by invading the non-fictional world – interrupt not a theatre rehearsal but a meeting in an editing suite where a squabbling team of film-makers are in dispute over how to complete their drama documentary about an English boy who sought and gained euthanasia in Norway.

When I saw the show in Chichester, I found myself concentrating on the way this adaptation raises updated Pirandellian questions about the ethics of using actors in the paradoxical process of making a documentary look more real. Here, on second viewing, I was just as impressed by the way the particular nature of the framing documentary strikes deep into the fraught family situation of the six characters, with its tortured story of children driven to suicide because of sexual abuse.

Ian McDiarmid is in superb form as the creepy Father, at once scalpel-like in his scathingly donnish autopsy of the situation and loftily and unloveably self-justifying. As it spins into a vortex of legitimate self-reflexiveness, this is a show full of coups. There's a stunning close to the first half where the family let rip in a berserk pastiche of Italian opera that skids dementedly between buffo and verismo – and which makes the point that "naturalism" is an inadequate means of expressing their truth. And there's an amazing sequence where the documentary director (Noma Dumezweni, excellent) feels her own sense of reality ebbing away. Vainly seeking help, she's filmed carrying the dying boy into the production of Les Misérables next door and is ignored by all the flag-waving folk on the barricades.

The National Theatre's revival of its own extraordinarily moving production of War Horse manifests the same qualities as Six Characters – absolute faith in the material; absolute faith in the good taste of the audience (for people aged 10 to infinity); and the determination to invest more money in the show to make it even better. As with Six Characters, the technical side of the show now surpasses itself. And those sublime horses – to call it puppetry is a bit like calling what went into the Sistine Chapel grouting.

Yes, it's a shade sentimental – but it's also ennobling, as we see the nervous system of these sensitive creatures punished by their enforced involvement in the horrors of the Great War. The great thing, though, is that the show is not an easy slur on mankind – it gives hope, not least in the exquisite way that, during the curtain call, the horse puppets, while rightly cheered to the rafters, get second billing to the people.

'Six Characters' to 8 November (0870 040 0046); 'War Horse' in rep to 24 January (020-7452 3000)