Few things are more readily guaranteed to sell out a theatre than the phrase “this play is not suitable for children” and Rufus Norris’s continued gamble in his first National Theatre season is that Cleansed should fill at least the Dorfman. It will, but for all the wrong reasons.

First is the notion that Sarah Kane is any sort of playwright deserving of national memorialisation. As a confused and angry seventeen-year old she embraced and later rejected born-again Christianity, and her works are a chronic mix of rage, impotence and wincingly simplistic homily – so love is good and torture is bad: as though you couldn’t read that on the triceps of any clown in a tattoo parlour.

Talking of which, by committing suicide in a hospital toilet she peaked as early as Amy Winehouse and so can’t challenge any of the statements made about her, including the three unpardonably pretentious pages by some polytechnic lecturer in the Cleansed programme.

So if you come cold to Cleansed, what will you find? A grimy basement set, a series of anonymous barefoot characters in grey suits routinely tortured by anonymous barefoot characters in black suits and watched by what looks like Josh Widdicombe in a red frock. It isn’t, it’s actress Michelle Terry (soon to play Henry V) who comes as close as anyone in the play to a credible characterization but her briefly lucid sequences serve only to highlight the opacity and obscurantism of the rest: at no point does anyone explain why people are being tortured, by whom, or what information is sought from them.

It’s cartoon Kafka for the Reservoir Dogs generation, and Katie Mitchell‘s lengthy and over-elasticated production wastes endless stage time orchestrating the repositioning of trolleys full of surgical instruments, the origami folding of plastic sheeting and clearing up with the thoroughgoing enthusiasm of a Cillit Bang advert.

Besides, the torture is laughably inefficient: an overdose of smack injected via an eyeball may be gruesome but a venous system full of complex opiates doesn’t make for coherent confession any better than cutting out someone’s tongue – although that character has post-operative dialogue which is even more strange, and scarifying the hands or feet of your victim using an abrasive wheel for ‘while you wait’ key cutting and shoe repairs seems both messy and ineffectual.

Not by way of any kind of research, but I seem to have visited a number of venues used historically for torture – and if I learned anything at the House of Terror in Budapest, or Auschwitz, or Tuol Sleng prison in Cambodia it’s that information is most easily extracted with electricity and a bucket of water, anything else is gratuitous sadism.

It’s not often an audience emerges almost unanimously saying ‘what a load of rubbish’ to its neighbours, but the opinion was widely shared:  from a teenage school group to one immaculately coiffed and manicured older lady who said ‘I’d rather sit through Evening At The Talk House again, and that was bloody awful’.

Mr Norris, and your audience feedback team: take note.