Every morning, Monday to Friday, I get up at 7am and make my wife breakfast in bed. She always wants something salty. I enjoy doing it because the rest of my day may be self-interested. I then walk for 15 minutes to a studio once owned by the artist Mark Gertler. Here, in 1916, he painted his antiwar masterpiece The Merry Go Round.

The day depends on whether I’m writing for stage or screen. If stage, I’ll putter through a couple of newspapers online, then start writing dialogue, ideas or maybe structural charts in a sketchbook that I get from an artists’ supply shop. When I’m ready I’ll transfer what I have to the computer and rewrite. My handwriting is so bad that sometimes I can’t work out what I’ve scrawled. If I end up with just a few lines of dialogue, it no longer panics me. All time spent considering your play is well spent, regardless of outcome. One day you write nothing, the next you write eight pages. It’s not in your hands. At lunchtime, I’ll go down to the local deli to get a pork pie or a bagel. If the writing is going well, I’ll continue into the afternoon. If not, I’ll go to the cinema or answer emails.

It’s only second-rate directors who lock the door of the editing suite so as to pretend they are auteurs

Life is different when writing for the screen. For every hour you spend writing a screenplay, you spend 10 hours defending it. Because you are the person who first proposes what the eventual film should be, you are likely to have to deal with 50 people who, usually from the best intentions, imagine something else. A film is a carnival of opinion, and if your view is to survive, you need the skills of an advocate. Screenwriting is more lawyering than writing.

On such days, I am likely to get on the tube to spend hours in meetings, usually victualled with stale sandwiches and a token orange. Producers fall into two categories. The great ones make suggestions to help you realise your work more fully. The annoying ones tell you at length how they themselves might have written the story, if only they could write. I have one simple rule. Only those who are invested in the outcome are allowed to give advice.

What this means is: when you write a screenplay, all sorts of people will want to fantasise their preferred version. But are they on board to be the people who actually make it? If you finance a film you have a perfectly legitimate right to argue about how it might be improved. But dilettante script editors and Bafta club bores who feel entitled to judge a script without the courage to commit to it are a waste of time. It’s simple. You have to buy chips to sit at the table.

The hardest thing in film is distinguishing between good and bad input. The whole point of writing screenplays is to provide a platform from which a director, actors and cinematographer will be able to leap to create something infinitely richer and more suggestive. You have to excite your colleagues. If you are too prescriptive in what you write, there is no room for their genius. But if you do not fight for your structure and underpinning, then everything will go to hell in an inchoate mess of actors’ improvisation and directorial overreach.

The joy of the performing arts is in collaboration. If there is a better way of spending a day than watching Carey Mulligan or Bill Nighy or Billie Piper perfect their performances, I have yet to find it. It’s exhilarating, but also instructive. When good actors rehearse, they test the ground, showing you or telling you where your own work is boggy. This is the glorious payoff for the hours you spend alone. Good actors illuminate everything.

Intelligent directors then welcome the writer into the cutting room, because a film editor does exactly the same job as you. They define shape, structure, theme and character, while driving narrative – only they happen to do it at the end of the process, not the beginning. It’s only second-rate, defensive directors who lock the door of the editing suite in order to pretend they’re auteurs. I avoid any director who, metaphorically, sweeps around the set in a cape.

Lately I’ve worked with youthful directors – Robert Icke in the theatre, and SJ Clarkson in television. In both cases it’s been pure pleasure, partly because their younger perspectives have deepened my scripts, but also because they both have a fabulous sense of humour. The surprising thing about a writer’s day in film and theatre is how much of it we spend laughing.

In Brief:

Hours: mornings always, afternoons when useful

Words: a play may take eight weeks, it may take two years

Time wasted: it all contributes

Drinks: a pot of coffee to last the morning, tea at 5pm

