Michael Lesslie started writing plays when he was just 15. In the two decades since, he has worked on feature films, theatre productions and TV dramas – from the 2015 adaptation of Macbeth starring Michael Fassbender and Marion Cotillard to a six-part series based on John le Carre’s novel The Little Drummer Girl, which aired on the BBC last year. Here, he offers some advice for aspiring scriptwriters – and explains how he went from reading scripts at the National Theatre to working with acclaimed director Park Chan-wook

Share your scripts – and read other people’s The National Theatre has an amazing resource where they read every script that is sent to them and give feedback. I sent mine in, and they called me and said, ‘this is awful, but you’ve got something – maybe you could come in and have a part-time job reading the scripts?’. So I spent a summer in the script room and it was my job to articulate why a script wasn’t working. It was the best education in the world, in a way – thinking about these scripts and how they could [be improved] and having to put that into words was really helpful and it made me want to write.

I still get really excited by reading other people’s work. No one person can write every single story and I think opening yourself up to other people’s voices and experiences can only ever improve [your own writing].

Get a mentor, if you can When I was at university, the playwright Patrick Marber was coming to town as a visiting drama chair, and he put a note up on the drama website saying, ‘I’ll read anyone’s play if they send it to me’.

I didn’t have anything that was good enough to send to him so I spent two weeks writing this script, sent it in and didn’t hear anything back. Six months later, he was visiting again and he got in touch. I went to meet him, and he pulled out my play and it was covered in his notes. His words were literally, ‘this is shit – but you are a writer and I’m going to teach you how to make this good’.

That absolutely changed my life, and I owe Patrick Marber a huge debt. I think the biggest way it helped me was just having someone say, ‘you’re a writer’. It seems so implausible when you’re starting out, that you could actually do this … so that was a huge thing for me.

Patrick was also good at giving business advice … and he really helped me learn the craft of stage and screenwriting. And it is a craft: there is a grammar to it, and you can break that grammar – that’s where most of the exciting work in every generation comes from – but I’m a big believer that you have to know the grammar to break it, or break it in a way that’s interesting.

There’s no way of denying it – my first commission came through having met people. But I think a lot of this industry is trying to meet people and prove that you can be collaborative.

Get to know people Off the back of [the script reading job at The National], I did some internships, and one of them was at the Donmar Warehouse where I worked with the casting director Anne McNulty. I kept going back and helping out … and while I was there, Nick Frankfort and Tobias Round, the Executive Producer and General Manager there, left to form a West End producing company. I had been doing script reports for them and they wanted someone to do something on the cheap, so they said, ‘We’ve got the rights to [indie film] Swimming with Sharks. There have been a few attempts to crack it for the stage, but they haven’t really worked, because it’s got quite a complicated flashback structure and it’s quite cinematic. Would you be up for having a go?’

I got paid peanuts for doing it but it was a massive opportunity – I got that commission the day I left university and around seven months later it was on the stage with Christian Slater and Matt Smith and Helen Baxendale.

There’s no way of denying it – my first commission came through having met people. [Frankfort and Round] thought of me because I’d been doing scripts for them. But I think a lot of this industry is trying to meet people and prove that you can be collaborative.

Be willing to collaborate… The writing process is different with every project. But in theatre, the writer tends to be the authority…. There is quite a lot of you going off, sitting in a room and then delivering a script and that’s the starting point [for a production]. There are development people who will help you [refine] it and you will always collaborate with the director and get [their notes], but that process is way more pronounced when it comes to working for the screen.

[With TV and film], it oscillates between periods of utter solitude, where you’re getting that first draft ready, and then you share it and that begins a long back and forth where you give it to development execs within the production company who will give you notes on it. You decide whether you want to engage with those notes, but a reality of the screen industry is that even if it’s your work, if you’ve sold it to a production company, and they fundamentally believe in notes that you’re not going to [respond to], they can fire you and get someone else.

A script will iterate many times as it goes through development execs, actors, producers, directors … and then when it goes into production, should you be so lucky, you have to collaborate and [respond to] restrictions. If a set designer says, ‘I know you’ve written 100 horses here, but we only have one’, then you might have to rewrite. Each time, you’ll go away and write your own prefaced version of [a script] and that gets tested against necessity and other people’s opinions so many times in film and TV. But I love that. I fundamentally believe collaboration makes my work better. You have to pick your collaborators of course, but I think the collaborative element is one of the most exciting things about being a screenwriter.

…but beware of just giving in When you get a break, you’re so grateful and so desperate to get stuff up and running – and this continues throughout your career (someone told me recently that 82.5% of commissioned scripts never get made, and that’s commissioned scripts) – so when you get the chance for that to happen, you’re so eager to please that there’s a real pressure to perform [the change] that people are asking of you.

Whilst you’ve got to be collaborative, [that] doesn’t always mean giving in or doing what someone else has told you. You’ve got to respect other people’s opinions and engage with them but also stay true to your instincts and your voice. One of the trickiest things about collaborating is holding on to your vision through a process where many other voices will be added to the mix and ultimately you don’t have the final authority unless you’re also a producer on the show.

It’s really important to live a life outside of screenwriting

Be patient You need to be resilient [to be a scriptwriter], and you need friends and family around you. I know it’s a corny thing to say, but it’s very hard to maintain self-esteem when 82.5% of your life’s work isn’t getting shared to the wider world, and it’s hard to remain confident that what you’re doing is good or even valuable. I think that’s true of people no matter how high up you get. And I think that’s another reason why it’s great to share your work – even if the feedback isn’t great, getting a response from someone is really gratifying.

Maintain a life outside of work There are definitely periods in my career where I’ve gone down a very isolated hole but I think it’s really important to live a life outside of screenwriting and outside of what you’re focused on. I find some of my best work comes when I’m not fixated with the industry, because then you’re making yourself relative. You’re comparing yourself to other people and you become imitative. Trying to do something that’s truly original and truly your voice is really hard and I think it’s important to find a life that’s not entirely based in the screen world in order [to do that]. You’ve got to be meeting people – people who aren’t just in the film or the stage business.

Take time out Any one of my friends and family who read this will laugh hard at this because I’m a workaholic. But sometimes, taking time out is the best thing you can do for a script.

Regaining objectivity on your own work is one of the big challenges for screenwriters. When I started out I would work obsessively until something was done and then hand it in straight away, and actually it was Patrick [Marber] who said to me, ‘You should put the script in a drawer for a month and come back to it later’.

If you’ve just sent off the work [without revisiting it], you’re way more vulnerable to [criticism]. If someone says, ‘we don’t like this’, it’s like a knife to the heart. You also have no objectivity on the script at that point – you don’t know whether it’s good or not.

You should always be writing as many stories as you can, because the more you are betting on a single script getting made, the more you are diminishing your odds

Now, what I try and do is write a script, leave it for a week while I write something else and then come back to it, and I try and incorporate as many of my own note processes into the first draft as I can so that when I hand it over to people, it’s as good as it can be.

Don’t panic if you hit a wall I know how it feels, when you’ve hit a wall and you think, ‘I don’t know how to improve this. I don’t even know if it’s any good or not anymore.’ [If that happens], I’d suggest either take time off or write something else.

You should always be writing as many stories as you can, because the more you are betting on a single script getting made, the more you are diminishing your odds, and also, people can end up liking scripts that you’ve done where you think, ‘really? That one?’ all the time. I think if you keep writing stories, that will help the other stories you’re writing.

Lesslie also worked on the 2015 adaptation of William Shakespeare’s Macbeth, which starred Michael Fassbender and Marion Cotillard

Finish before you revise… One of the processes I have, and I’m not alone in this, is that I will draw up a very loose structure – a sort of three to five page outline of what a script should be – and then I do ‘the vomit draft’, where I’ll write every day, and then come in the next morning and write some more, and I don’t read over what I’ve done – I just keep going until I’ve got to the end, and then I can take stock.

Getting the first draft of something out is the most painful and scary process, and I know a lot of writers who will approach things thinking, ‘right, I’m going to work scene by scene and get each word perfect’, but I fundamentally believe that no word is perfect without context, and you’re never going to know the context [without writing the whole story]. Getting to the end is really important, and then you can go back and make it better.

…but know when to call it quits If you have no more energy for something, if you’ve fallen out of love with it, give it to someone else. You have to maintain passion for something – as soon as [you’ve lost that], you’re not going to be doing your best writing, and no-one’s going to benefit from that.

Lesslie co-wrote the screenplay for Assassin’s Creed, the blockbuster film based on the game of the same name

The future of TV I think [the growth of streaming platforms] is pushing people to two extremes. It’s created this whole glut of material that is like comfort viewing … where people don’t want to be challenged. The whole phenomenon of second screen [using another device while watching TV] has become its own kind of entertainment, and [led to] work which falls more in the opiate category.

But also, because there’s all this stuff, and because audiences are quite drawn to saying, ‘I want to watch something mindless’, it’s also pushing people towards going ‘well, OK, to capture their attention, I’ve got to do something bold, but also entertaining’. In a lot of art house cinema, which I love, people tend to sacrifice entertainment, but my number one films and TV shows do both. They’re ambitious and emotionally complex and morally difficult, but they’re also entertaining.

What I hope is that [the arrival of] streaming platforms also breaks up the predictable format that we’ve got used to. I hope mini series become celebrated on streaming platforms, and movies … because not everything has to be a 22-part returning series. Obviously that generates more income for the producers, but sometimes, stories should reach their end.

The Little Drummer Girl is available now on iTunes and released on DVD on January 28.