Will Sharpe & Tom Kingsley: Chris Langham was our first choice

The actor is not a paedophile, has done his time, and was the best man for the job. Can we talk about our film now?

Black Pond is our first feature film. We're 25. We made it for £25,000. The critics who have seen it so far have all said very nice things, but a lot of the press has focused on the fact that the film stars Chris Langham: Bafta-winning star of The Thick of It and Help, subsequently sent to prison for downloading indecent images of children. So, as you can imagine, we've been asked a lot about why we cast him and whether we realised what that would mean.

Long before we decided to try to make a film, the story of Chris Langham was one that we were aware of. We admired his work, so we followed the horrifying coverage of what he was alleged to have done. From reading the papers, we first assumed that he had abused children, that he had a history of sexual interest in children, and that, at the very least, he must have paid to download child pornography. If that had been the case, we wouldn't be writing this article.

But none of those things are true. The judge made a point of saying that there was nothing in the papers before him to suggest that Chris was a sexual predator, and that paedophilia was not an issue in this case.

The UK's foremost authority on child abuse testified in court that he was convinced that Chris is not a paedophile, as did an eminent psychiatrist who is also an expert in this field. These facts have generally been ignored by the tabloids: it's more exciting to print fiction about a monster, than it is to print facts about a human being.

As we read more about it, it gradually became clear that Chris was in fact someone who had made a mistake, who had paid the price and who should be allowed to move on and make use of his obvious talents. Armando Iannucci, quoted in The Independent on Sunday, said: "There is a terrible absurdity about his position, in that what shapes your life is not what you do but how the media chooses to portray you." Not many others from the industry have defended him publicly, but is that a surprise? If being popular is how you make a living, it's a bad idea to put your popularity at risk. Nobody wants to seem like an apologist for paedophiles.

We do not condone paedophilia in any way. It's a serious issue. But the discussion of the rehabilitation and reintegration of paedophiles is a separate issue to the discussion we should be having about Chris Langham.

People are, of course, entitled to think whatever they like, but we believe that Chris Langham is not a paedophile. It was our belief before beginning to write the film. And, having done our research and having met him and his family and worked with him, it's a belief which we feel is completely justified.

Chris Langham was sentenced for the offence of downloading 15 free images of child pornography, of which he had viewed four. For what it's worth, at the time, he said it was like "putting my face in a chainsaw". And Chris himself condemns his own thoughtless and stupid actions as harshly as anyone else, as indeed do we.

In an interview in The Guardian last week, he apologised for his actions and he's spoken numerous times in the past about how much he regrets what he did. But we're learning pretty quickly about casual misquoting, the frequent breaching of editorial guidelines, and the art of needless spin. Only last week, for example, much was printed about how Chris "thought he would be admired" for his research into the subject. The quote was taken out of context. The point he was making was that, looking back, he realises that imagining he would be admired was an inexcusably misguided and idiotic way of thinking.

We didn't take this decision lightly. But the more we looked into it, the clearer it became. Yes, Chris had broken the law. But he had served his sentence. So we didn't think it was an immoral thing to do, to cast him.

Sure, we both had people warning us against it. But funnily enough it was never: "Don't do it because he's a paedophile." It was always: "It's a really sad state of affairs. Who knows what really happened? He's a terrific actor, but it's just madness to cast him. The press will tear you apart."

Well, we don't regret it for a second. After the Guardian article came out, we were overwhelmed with positive feedback and a moving amount of support for Chris and for his return to screen. And our experience of Chris has been that he is a good man. He cares deeply about his family. He's a loyal friend and a committed sponsor to many in Alcoholics Anonymous. He worked hard and generously on set and was a pleasure to work with. The other really crucial thing is, he is brilliant. The kind of brilliant that you can't fake. He's an irreplaceable talent. And perfect for the role of Tom Thompson.

It's normal when you're writing a script to talk about who you imagine playing the parts. It's half a living-room daydream kind of thing ("We could get Dustin Hoffman!") and half a serious attempt to plan ahead and make sure everyone's on the same page about who these characters really are. Chris Langham was one of our hypothetical Tom Thompsons from the beginning. The part is of a bumbling middle-class father in a dysfunctional marriage: in a sense, we probably said, what Hugh Abbot (from The Thick of It) might be like if he went home.

When casting the film, we knew that Tom Thompson, one of the leads, was an important part to get right. We tried many actors, with a lower profile than Chris, calling their agents and trying to disguise the fact that we were 24-year-old nobodies. And then we thought: Why don't we ask him? It may seem pie in the sky, but what if he said yes? He would be perfect. And he did. We sent the script. He liked it. We met. We told him we didn't have very much money. He was OK with that. He was just happy for the work and the fact that he liked us and our approach to the film was, in his words, "an unbelievable bonus". We were delighted.

We cast Chris because he was the best person for the part. We cast him in spite of the publicity, not because of it. Yes, we want to publicise the film. Yes, we want people to hear about Black Pond and to go and watch it but if Peter Andre had said: "Hey, I heard about your low-budget script... I really want to play Tom Thompson..." (unlikely, true, but...) we wouldn't have said yes just because he was famous. We cast Chris for the same reason we cast Colin Hurley, Amanda Hadingue, Simon Amstell and everybody else – because he was right for the role.

Making a feature film on a tiny budget means you have to work as a team. Chris was as much a part of that team as anybody else. We're all really proud of Black Pond. We think it's time to shift the focus back to the film. We hope you enjoy it as much as we enjoyed making it.

Paul Vallely is away

'Black Pond' premieres at the London Raindance Film Festival tonight, with a further screening tomorrow. It is released on 11 November