MILLY Thomas was waiting to go onstage when she first read the script for the pilot episode of Clique, BBC3's Edinburgh-set university thriller created by Skins alumni Jess Brittain. The actress had been put up as a possible writer on the glossy six part drama and Thomas was initially sceptical, but after her dressing room read-through, she was smitten.

“I couldn't stop thinking about it,” says Thomas, who has two original plays on the Edinburgh Fringe, in one of which she performs. “University was probably the worst four years of my life,” she says. “and all the writers had terrible times at university, do the three of us were like a support group.”

Thomas went on to write three episodes of Clique and then for BBC Scotland's River City and now she has to Edinburgh shows to enthused about. Brutal Cessation looks at the fallout of an abusive relationship, and in Dust, Thomas plays a woman observing her own suicide. Both plays come from a personal place.

“Last year I was in a relationship that wasn't necessarily right for me,” Thomas says of the roots of Brutal Cessation. “I wanted to look at how gendered things have become, and how relationships that should have ended a long time ago can end up on a knife-edge of violence and emotional abuse out of sheer boredom.”

Dust comes from a similar desire to lay bare taboo subject matter.

“I'd had the idea for Dust for ages,” Thomas says, “but I was really frightened of it, because I knew I was going to have to be in it. It's a really personal piece, which in part came out of my fascination with the way we talk about people with depression, and how we can sometimes eulogise them. I've been depressed for so long, but because I'm high-functioning, people don't notice. As a playwright, of course, I want to entertain, but I write about what I don't know. I tried to write about what I do know, but it sounded patronising. When I write, I want to find out about things, so I can discover them together with the audience.”

Thomas is onstage in Dust at the same time Brutal Cessation is being performed.

“I did that on purpose,” she says. “Once I get up to Edinburgh, my work as a writer on the plays will be done. There's nothing worse than having a writer around, biting their nails like the ghosts of Christmases to come.”

Thomas grew up in Hampshire, and wanted to be an actor from an early age. Her first play, A First World Problem, appeared at Theatre503 in London and Piggies and Clickbait followed so that, between appearing onstage and on TV in Downton Abbey, Thomas became a member of the Young Writers Lab at Soho Theatre, and took part in a Royal Court Writers' Group led by playwright Stef Smith. Clique followed shortly afterwards.

“When I got Clique, I didn't know if I could write for telly,” Thomas says, “but that naivety's really important. If I know things too well I get worried. If you don't know the rules, you can break them, and that flailing doggy paddle is where the magic happens.

“The great thing about Clique is that it's a female driven vehicle, and all the women in it are having these seemingly wild lives. At it's heart it's about female friendship, ad I wish I'd had that at university. Apart from everything else, it's also sending out a message that you can have stories led by women who aren't necessarily nice to each other. I think what Jess has achieved is astonishing, and I knew as soon as I read it that there wasn't a thing I wouldn't do to work on it.”

Whether or not there is a second series of Clique, there are plans for a new stage play,

It is a lot bigger than anything I've done before. People who know my work know me for writing sarky women, but this is different. I just want to keep on keeping on. I don't ever want to stop acting or writing. They're my favourite things in the world, and I want to keep trying bigger and better things all the time. I hope to keep on writing until I drop dead.”

Dust, Underbelly, to August 27; Brutal Cessation, Assembly, to August 28.

www.underbellyedinburgh.co.uk

www.assemblyfestival.com