Interview: Mark Haddon

Of all the sins a stage adaptation of 'The Curious Incident of the Dog in the Night-Time' could commit - and there is, Mark Haddon observes wryly, no limit to the ways in which you might screw the job up - the one he fears most is 'excessive sentimentality'.

This says much about the author's relationship with a novel that, in 2003, won nearly every award going for both children's and adult fiction, and went on to become the bestselling novel by a British writer of that decade (not to mention, as Haddon recently discovered to his amusement and unease, a recommended text for social workers and police officers looking to understand autistic spectrum conditions). It is now headed to the National Theatre, in a highly physical new adaptation by Olivier Award-winning playwright Simon Stephens.

'“Curious…” is like smallpox or something,' says Haddon of the slim. playful book about a 'mathematician with some behavioural difficulties' (as 15-year-old narrator Christopher defines himself), who sets out to investigate the violent death of his neighbour's dog. 'It's sort of lodged itself in the human population, for better or worse, and become part of the cultural wallpaper. I've killed the book stone dead for myself by talking about it too much. So one of the purely selfish functions of this adaptation is to make it exciting for me again.'

To this end Haddon only attended the first rehearsal for the NT's production, which will be staged in the round by 'War Horse' co-director Marianne Elliott, with movement directors from physical theatre company Frantic Assembly. He had no input in the casting of Luke Treadaway as Christopher, though he does say that 'one of the joys of going to the theatre is seeing a really great actor being someone entirely unexpected'. With Stephens, a friend, he's mainly been talking about maths.

'Initially I thought there would be a fundamental problem about how you staged a novel that was located almost entirely in the mind of someone who could not communicate,' he says. ' But when he got down to writing he realised the book is actually very theatrical, because the dialogue is so terse and minimal.'

And has Stephens kept the swear words, dutifully reported by an uncomprehending Christopher, which led to calls for the book's withdrawal from children's sections? 'Simon's added a few more. I don't think Simon's capable of writing a play without some kind of profanity.'

It never crossed Haddon's mind to adapt 'Curious…' himself ('for the same reason that surgeons aren't allowed to operate on their own children'). But he's a long-term theatre lover who debuted his first stage play, 'Polar Bears', at the Donmar Warehouse in 2010. Although Haddon's co-promoting his new novel, 'The Red House', he asserted in a recent blog on his website that 'contemporary British theatre is so much more vital than the contemporary British novel'.

'There's an innate conservatism in a book that wants to entertain 30,000 people,' he explains. 'If you're writing for the subsidised theatre in London, you have so much more freedom.'

Whether or not you choose to label Christopher as having 'Asperger's Syndrome' (as the early book jackets did, much to Haddon's regret), the publication of 'Curious…' coincided with, and arguably contributed to, a huge leap in general understanding of autism spectrum conditions. But theatre has lagged behind. Last summer two young boys with autistic spectrum conditions were asked to leave London productions of 'Wicked' and 'Shrek' for making too much noise. Spurred into action, the NT will be having a special 'relaxed performance' of 'Curious…'.

Haddon has spent a decade avoiding commenting as an authority on anything relating to Christopher's 'condition'. But he's clear on this one: 'It's always great to get more people into the theatre, whoever they are and however they behave, and there should be many more performances for people like that. I think the most irritating thing for actors is those people who buy the expensive seats and like to have a nap in the middle of the play. I'd personally kick those people out instead.'

And if the NT starts taking group bookings for social workers and police officers? Haddon laughs, thinks, then sighs the sigh of a writer who, for the second time around, has said all they have to say.