Pick up a different screenplay each day this week when you purchase The Times at WH Smith, or send away the form on page 34 of Monday's edition of The Times. Monday's script is The Queen, followed by Shakespeare in Love on Tuesday, Billy Elliot on Wednesday, The Hours on Thursday and Trainspotting on Friday.

A dramatist and screenwriter, David Hare, 60, was nominated for an Oscar and a Bafta for The Hours (2002). His plays include Stuff Happens (2004) and, this year, The Vertical Hour at London’s Royal Court Theatre (showing until March 1). Forthcoming films include The Reader, My Zinc Bed and Murder in Samarkand.

In my view, anyone who writes a screenplay will have to face the fact that whatever they write will invariably disappoint the other people working on the film. If you ask me what a screenwriter’s job is, then I would best define it as managing disappointment.

Let me explain. Until the screenplay is written, then everyone involved in setting up the movie – financiers, producers, director – all think that they are talking about the same thing. A film that is yet to be made is, if you like, a collective fantasy, and it’s in the nature of fantasy that everyone sees it differently. Until they have the written scenes in their hand, every contributor has their own vision of what the final work is going to be. It spools out in their head, and of course it’s perfect. So it’s only when the screenplay arrives that there’s this inevitable moment of grade A disappointment. Everyone involved says: “Oh my God, it’s not going to be everything, it’s going to be something.” We all know that at any kind of meeting – be it political or business – you never want to be the idiot who speaks first. Because everything you propose is, naturally, going to be opposed. Otherwise you wouldn’t be having a meeting. Well, that’s who the screenwriter is. He’s the poor sap who puts up the initial ideas for everyone else to knock down. And the director, if he has final cut, or the financiers – more often – are the lucky bastards who get to speak last. They get to sum up.

Of course the low status of the screenwriter is an industry joke, but it’s a joke that can get a little bit tiresome. At the moment I’m working on a film of Bernard Schlink’s great novel The Reader. A couple of days ago, I found myself standing outside my hotel in the howling Berlin wind at eight in the morning, waiting for nonexistent transport, because, yet again, the production had forgotten that the screenwriter existed. If you buy one of those computer kits that provides a template for how to produce a film, then you won’t find the screenwriter’s name on the daily generated call-sheet, because as far as the format goes, you never even happened.

Having said all that, my experience on The Hours was more or less a model of good practice. The producer, Scott Rudin, and I worked together without a director for about a year. Then, when we felt the script was ready, we put it out and said to potential directors: “This is the film we want to make.” Scott gave it to a couple of people who said: “Well of course I’ll be wanting to do some work on the script,” to which Scott replied “No. This is the script we’re making.”

Now in fact, it didn’t work out like that – it never does – but it meant that when Stephen Daldry joined us to direct, he accepted the basic structure, he accepted the complex time-jumps, the elisions between the three stories, the thinking behind the screenplay, even if it was two more years of refinement and adjustment before we locked off the final film.

That’s how long The Hours took – three years. And Stephen and Scott had one basic insight into screenwriting which most people lack. They saw the screenplay as a continuous process. Not only was the screenwriter welcome on set to continue the work with the actors in person, but, just as important, they regarded editing as merely a continuation of writing.

So I was there through the countless reedits, I was there when the music was put on, and I was there when the film was finally locked off.

A lot of people told me the book was impossible to adapt, so I was always slightly freaked by the fact that I couldn’t see why. Yes, of course Michael Cunningham’s novel was mostly interior monologue, so it was obvious that I had to invent scenes that would express what the novelist was able to do by description. But, for me, that was the excitement of the job, the challenge.

However, even I could see that the real trick was how on earth we were going to put over such apparently uncommercial material to a large audience. That, I think, was Stephen Daldry’s genius: he made a film about Virginia Woolf, lesbianism and suicide which crossed over to become a hugely popular film. I still don’t quite know how he did it.

You have to remember, art films which break out of art-houses are very, very rare. And British ones are even rarer. It’s what you dream of. When The Hours happened, there hadn’t been one since The English Patient. And I’m not sure that there’s been once since – not on the same scale. There was a bizarre moment when I even saw it playing on three out of four screens in a pop-corn multiplex in California. And even more extraordinary, the original Virginia Woolf novel Mrs Dalloway, on which The Hoursis based, climbed to No 1 in the US paperback chart. No academic, however jealous, could disdain a medium that drives the modern reader back to Virginia Woolf.

I suppose The Hours taught me that the definition of a classic is one where the audience knows the film better than you do. Normally, when I’ve worked on a film, I know it better than anyone else. Indeed, usually I’ve been the only person who knew it at all. But with The Hours, wherever I go people remind me of their favourite scenes or moments that I’ve completely forgotten. And I admit I haven’t watched the film since we made it. You see, I know it would disappoint me.

Because in my mind, it’s everything. But if I actually watch it, it’ll just be something. That’s the nature of film.

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