Mark Haddon's one-off drama explores how Down's syndrome affects family life.
Mark Haddon's one-off drama explores how Down's syndrome affects family life.

BBC1's new single drama Coming Down the Mountainis special in several ways, most notably because it stars a teenager with Down's syndrome in a lead role. The character of Ben (played with terrific conviction by Tommy Jessop) is an increasingly intense role, prominent throughout the 90 minutes.

The story reaches its climax on a ridge near the top of Mount Snowdon, a location fraught with technical difficulties. Above all, perhaps, it is unique because it is a first screenplay by award-winning novelist Mark Haddon, a fact which seems to have brought rewards and challenges in itself.

The film is also a first for producer Roanna Benn. A script editor and executive producer at Tiger Aspect for 11 years, she had only ever actually produced a short Comedy Lab piece for Channel 4. A fan of Haddon's The Curious Incident of the Dog in the Night, she approached him with a different proposal after hearing a short version of Coming Down the Mountainon BBC Radio 4. 'Mark didn't want to do our project. He just does his own thing,' Benn recalls. 'When I said I loved the radio play, his agent said it was the one thing he would do for television.'

Unusually, the play looks at the effect of having a child with Down's syndrome on the rest of the family, although Haddon maintains the emotional dynamic would be much the same if the child was special in any other way - a junior tennis champion, for example.

In fact the lead character is Ben's brother David, played with conflicted sensitivity by Skins star Nicholas Hoult, who feels that Ben's presence in the family has ruined his life. This comes to a head when the family moves to the north so that Ben can attend a special school, destroying David's relationship with the girl of his dreams.

The script was developed by Haddon, Benn and director Julie Ann Robinson, whose portfolio includes Cutting It and Blackpool and US drama Grey's Anatomy.

'We seemed to do draft after draft,' says Robinson. 'Mark was fantastic: unbelievably collaborative and patient, but very clear about his vision. You need someone like Mark who will fight back at times, not just go along with everything you say. The parts of the parents (Neil Dudgeon and Julia Ford) were particularly tricky, getting their dialogue comfortable and real.'

Haddon once worked with autistic children, but 'he plays that down a lot', says Benn. 'I think Mark just absorbs people.'

'Mark never ever uses research,' adds Robinson. 'He thinks things should come organically from within the characters.' Benn, meanwhile, could not risk offending viewers and sent the final script to the Down's Syndrome Association. 'They sent it back and it had no amendments!' she says.

The essential emotional accuracy of Haddon's script was confirmed by families during the lengthy process of casting Tommy. Casting director Jill Trevellick and a colleague saw 120 actors with Down's syndrome, workshopping with various possible Davids, in marathon sessions in London and Leeds. Tommy Jessop and the self-deprecating Nick Hoult had an instant rapport, she says, ' because Tommy found Nick so funny'.

Benn and Robinson began to get more and more feedback from the families of the actors with Down's syndrome about the emotional complexities of their lives. In one particular family, similar tensions to those in the script had led to a family tragedy. Robinson explains: 'They were very grateful to us for opening it up and talking about a situation they felt was common. We discussed their story with Nick and we were all very aware of it during the shoot.'

Tommy Jessop already acts in his mother's small theatre company in their home town, Winchester. It also helped that he turned out to have a 'photographic memory', says Benn.

Tommy's mother was incredibly supportive says Robinson, and was present on set at all times, always pushing him to do his best. A violent scene near the climax, 'was the only time I saw her flinch'. Robinson would stand next to the camera, talking him through his scenes and giving encouragement. 'I sometimes do that with ordinary actors, anyway, though.'

She does not believe in rehearsing television drama.

'It can deaden the performance. I try to find it in the moment. The stunts had to be rehearsed, including a fight scene involving Nick, but I like to let it happen on screen because you get intuitive performances. We did lots of takes and the ratio of film we shot to the length of the final edit was very high, but we would mould the performances across the takes.'

Haddon's script included about 55 separate locations, so the logistical problems were formidable. Apart from getting stuck in Hackney traffic jams, there was the matter of getting cast, crew and stunt doubles onto the top of Snowdon. Everything went up on the narrow-gauge railway, which opened specially out of season. For some shots, the cast had to be attached to safety wires, and the only way to make Hoult's hair look as if it was being blown about by a helicopter was to point the helicopter itself towards him, 'the most expensive hair-dryer I'll ever use,' Robinson jokes.

When the film was finished, Benn recalls, Tommy Jessop was asked at the press launch, how he felt seeing himself on screen. 'I've arrived!' he beamed. After this performance, he could turn out to be right.

TX: Coming Down the Mountain
Broadcaster: BBC1
Producer: Tiger Aspect
Start: Sunday, 2 September, time TBC
Length: 90 minutes
Commissioner: Jane Tranter
Executive producer, BBC: Sarah Brandist
Executive producer, Tiger Aspect: Greg Brenman
Producer: Roanna Benn
Director: Julie Ann Robinson
Writer: Mark Haddon
DoP: Danny Cohen
Casting director: Jill Trevellick
Key cast: Nicholas Hoult, Tommy Jessop, Neil Dudgeon, Julia Ford