5 minutes with: Indira Varma: 'Harold Pinter made sure you knew who the boss was'

I originally wanted to be a mime artist. I was really interested in the physical aspect of drama and I wanted to go to Le Coq. But I don't think I would be any good. English is my parents' second language and we used to go to the theatre a lot but it was generally to see dance, or mime festivals. So people like Nola Rae or Marcel Marceau. I thought it was amazing that you could express so much without words.

It was at drama school where I discovered language. But when I left, my first job was in film and I felt so disillusioned by it because I thought that, compared to plays, the writing was so poor. I realise now it's more of a visual medium, although obviously some filmmakers work with incredible scripts.

I got to work with Harold Pinter a lot, which was a massive privilege. He first directed me in Celebration at the Almeida in 2000. In rehearsals, you knew who the boss was, but he was the most generous, straight-talking, sensitive man and he loved actors. He said: 'If you're truthful, you can do anything'. And that was such a liberation.

It's really hard to summarise The Treatment because it's a Martin Crimp play. But it is about a girl called Anne, who has had an experience – I don't want to give too much away. She wants to share the experience and has called on film producers (of which I am one) to tell her story, and these producers are hungry for an authentic story. It's basically about when life becomes art, the need people have to create and our obsession with authenticity and truth.

I first worked with the director Lyndsey Turner when she was an assistant at the Royal Court. I knew, even then, that she was going to go far. She's frighteningly clever and is one of the most knowledgeable people – not just on classical stuff, but on popular culture too. She has made the show a bit David Lynch-esque. It's really dark but it's also very funny.

On first reading I missed so much in The Treatment. Crimp is such a master, there's a satisfaction in how difficult it is for us as actors because there's a lot of overlapping dialogue and simultaneous conversations in it. It's intricate and very difficult to play – it's a poem, in a way.

My character in Game of Thrones is really fun. When I started, it was a little like when I started working with Pinter – I didn't really know what a colossus he was, so I wasn't intimidated. And the same goes for Game of Thrones. The first time it dawned on me was when the costume designer talked about a detail in the costume on my neck. I pointed out no one would be able to see it, but she said: 'we'll know it's there'. That's the lengths they go to for the detail.

I was in Lucy Bailey's quite bloody Titus Andronicus where people fainted a fair bit. But I remember doing Twelfth Night at Wyndham's with Michael Grandage and one particular scene kept making people have heart attacks. It was when Aguecheek says "I was adored once too." He's a bit of an idiot then he says something very heartbreaking. And somebody had a heart attack at that point in the matinee and then again at the same point in the evening performance. They were OK, but it was extraordinary! Literally a heart-stopping scene.

The Treatment runs at the Almeida Theatre from 28 April until 10 June with previews from now.