I’m writing this from the set of a movie, which I also wrote. Not a great sentence, I have to say, for someone offering up his credentials as a writer, but there you are. It’s called The Infidel: it’s a comedy about race, about Muslims and Jews, and as such there was a fair amount of tricky stuff to negotiate in the writing of the script, but nothing as tricky, it turns out, as actually watching it being filmed.

The default position of a writer on a film set is, I should explain, not there. By rights I should simply be back at home fretting about how it’s going. The Hollywood attitude is clear: writers are the lowest of the low, dispensable in the development process and banned from set. All producers would agree.

Luckily, on this film, I also happen to be a producer, so unless I get confused and ban myself, I remain at liberty to turn up and undergo the trauma of seeing my ideas made flesh.

Calling it a trauma sounds absurdly ungrateful, given how many screenwriters never get their work near a film camera — certainly one without an automatic upload to YouTube button — but watching your imaginations realised really is stressful because for good or bad, it never corresponds exactly to what was in your head. The process involves continual compromise.

One previous film I know of where the writer was regularly allowed on set was Four Weddings and a Funeral. It was helmed by Mike Newell, a drama director, but Richard Curtis, the writer, was on hand the entire time to advise on the comedy. This is a wise move.

Comedy is a different language from drama. In some ways, it’s more like music. With a dramatic scene, you can film it in five different ways, and they all may be equally valid. With comedy, if you don’t shoot it right — if you don’t cut to the reveal at exactly the right time, or if the actor doesn’t leave exactly the right length of pause before the punchline — it’s not funny any more: it’s like playing the wrong notes.

But, in actuality, on a film set, especially a low-budget film set, the Newell/Curtis method is not that easy to apply. We’re normally trying to film about four or five pages a day: this means that it’s always a race against time, and the director always has a hundred things to think about. Going up to him and saying “I think it might be funnier if . . .” or worse, “I’ve just had this idea for a new joke . . .” therefore can result in a look rather like the one I believe Sam Raimi must have given to his star actress to help her to nail the face he wanted her to make just before vomiting up insects in Drag Me To Hell.

But on the whole, we are managing to work together. As a writer I’m pleased about this, and not just for practical reasons. I don’t hold with the way screenwriters have become culturally low-ranked. It’s a weird historical quirk, directly linked to the rise of the director — and the idea of the director as auteur — which itself is a product of the French nouvelle vague of the 1960s and the American behemoths of the 1970s. It was only then that movies begin to be titled A Martin Scorsese film, or A Steven Spielberg film.

The absurdity of titling films in this way is made succinctly by Joe Eszterhas, one of the few screenwriters who perhaps is as well-known as a director, in his book The Devil’s Guide to Hollywood: The Screenwriter as God. Eszterhas says: “It is not Steven Spielberg’s ET; it is not Sidney Lumet’s Network; it is not Sam Mendes’s American Beauty . . . it is Melissa Mathison’s ET; it is Paddy Chayefsky’s Network; it is Alan Ball’s American Beauty.” He lists about 20 movies. With most of them, the name of the writer was news to me. The person who wrote the script, the person whose idea it was: in the memory, uncredited.

Interestingly, this doesn’t happen so much in TV. With the highest-end TV, The Sopranos, The Wire, The West Wing, we have heard of David Chase, David Simon, or Aaron Sorkin (and Alan Ball, but only because he went on, after American Beauty, to write Six Feet Under) and, in general, have not heard of the directors. Cinephiles will blather on about how this is all to do with the particularity of cinema but really, the difference between the two mediums isn’t quite as much we would like to believe. Shows like this, which are made to play on widescreen TVs are very cinematic; meanwhile, all cinema ends up eventually on TV.

But what I’ve learnt through doing this movie is that Joe Eszterhas’s idea, although corrective, is not quite right either. ET is neither A Melissa Mathison Film, nor A Steven Spielberg Film. Film-making is an intensely collaborative process and everyone is vital: director, writer, editor, actors, cinematographer, location managers, sound engineers, set designers, electricians, caterers. Really, movies should be titled A . . . Film, inserting the names of all of these people, although this would probably not fit on the screen. And cut . . .

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