A naked man, with a generous paunch, jogs on to the tiny stage and starts rooting around in the kitchen cupboards for a cigarette. In yer face? Yes, uncomfortably so – and that's just the first few minutes of Belongings.
Morgan Lloyd Malcolm's debut play is an explosive tale of a young female soldier, Deb, who returns from Afghanistan to find her father (the naked one) shacked up with one of her friends and running a porn empire from the spare room. Pitting two men and two women against each other on a split stage – half Helmand bunker, half West Country kitchen – it's an angry journey into two macho worlds, both bristling with sex and violence.
The 31-year-old playwright spoke to female soldiers and hung out on Army chat forums to research the comic, tense and often shocking scenes set in the billet Deb shares with her male counterpart. The father's storyline grew out of a short play she wrote about a housewife who discovers that her husband has been filming their sex life and putting it online, behind her back. "I was thinking about all the different roles we play as women. On the one hand we're told we should be strong – to go out there and get what we want. And on the other, we're still trying to be mothers. And then we're trying to be sexy. There are so many mixed messages about what is sexy and what is strong, I wasn't really sure what women were supposed to be doing."
Bold and brutal, with shades of DC Moore and Simon Stephens (indeed the Punk Rock writer advised on the script), the play premiered last month in Hampstead Theatre's excellent Downstairs season where writers test out new work in the basement studio, away from the critical glare. This week, it will be the first to transfer to the West End, opening at Trafalgar Studios and making Lloyd Malcolm officially one to watch. In fact, a protégée of Kevin Spacey, she's been writing for years – most recently collaborating on Platform at the Old Vic Tunnels and the last two pantomimes at the Lyric Hammersmith – but tomorrow night will be the first time she sees her name in lights.
It was always destined to happen. Her mother, Judy Lloyd, played Ophelia to Frances de la Tour's female Hamlet while pregnant with her; her father, Christopher Malcolm, is a one-time RSC actor, who who starred in the original Rocky Horror Picture Show and now produces musicals. She wrote her first piece while studying Theatre at Goldsmith's, "a navel-gazing comedy about slobby students", which she took up to the Edinburgh Fringe "on a whim". That whim became a career as she formed a comedy trio, Trippplicate, with the actress Katie Lyons and director Verity Woolnough, performing "bonkers, slapstick stuff" and helped create E4's School of Comedy – an adult sketch show performed by children.
Increasingly stricken with stage fright, her playwriting career took off in 2005 when she was chosen to take part in the Old Vic's 24 Hour Plays. She produced a quickfire response to the 7/7 bombings –"But it was quite funny, it ended on a song" – which led to a fruitful relationship with the theatre's artistic director, Kevin Spacey. He has since commissioned Lloyd Malcolm to write his speeches and even a skit for the launch of a luxury Swiss watch in which he starred alongside Elliot Cowan as Leonardo da Vinci and Thandie Newton as Mona Lisa. "It was the most surreal moment of my life," says Lloyd Malcolm. "Kevin's been great – he's thrown work my way. You do end up in very odd situations. If I'm going to survive as a writer I need these extra strings to my bow. I've written every kind of thing you could possibly write and the one thing I want to write is theatre. But it doesn't pay very much."
Nevertheless, she's now writing her next play, Epidemic for the Old Vic Tunnels, and is working on a one-on-one promenade show, You Once Said Yes, where audiences choose how their story unfolds, which will preview at Latitude before going up to the Fringe.
She's also just finished a two-part television drama, Protective Headgear, inspired by a hit-and-run motorbike accident her father was involved in when she was seven years old. "Whoever did it, removed his helmet to check he was breathing, phoned an ambulance and left. They took his helmet, too. I've always wondered who that was and whether living with what they did has hurt them more than just owning up to it."
'Belongings', Trafalgar Studios, London SW1, to 9 July (0870 060 6632; www.trafalgar-studios.co.uk)