Alfred Jarry’s 1896 absurdist shocker Ubu Roi is one of those famous plays that never gets done, and that remains the case, really, despite Simon Stephens’s chilling courtroom take on the deeds of a tyrant who is a foul-mouthed buffoon and mass murderer.

What he and director Katie Mitchell have done is condense Jarry’s black farce in a Punch and Judy puppet show that tops and tails the sober proceedings of an international criminal justice court, as though Ubu was being arraigned in the manner of Ratko Mladic in the Hague.

The monster is called to account and his words recycled through the microphoned speeches of two impassive interpreters, so that the impact of the evening lies in the horror with which the madman is exposed, not – as in Jarry – the exhilarating delight in his grotesque escapades.

In other words, the play has been politicised, but in a different way to how it exists. There is nothing wrong in doing this, and Stephens writes as well as he always does, but the show is far less fun than it should be. It’s been given the old Tricycle tribunal treatment, and we’ve has quite a lot of that to be going on with for now.

I’ve seen the play once in Budapest and once in Paris, the latter production directed by Peter Brook with prodigious physical invention and a real sense of beauty, which only served to highlight the pell mell murkiness of it all. The puppets at Hampstead are quite fun, but the action is garbled, not executed, so you don’t get any of the schoolboy parodies of Macbeth and Julius Caesar.

Simon Stephens recounts in a programme note how he was inspired by trial of Charles Taylor – his lewdness, cannibalism and sexual energy are utterly ubu-esque – and is intrigued, and appalled, as are we all, by the revelations about Colonel Gaddafi and indeed Mladic. But a trial has a different sort of energy to a play, and this one seems slightly too po-faced and righteous for its own good.