Were Quentin Tarantino to guest edit an episode of Outnumbered, the results might be akin to this new twist on Medea at the Gate Theatre in Notting Hill.

Writers Kate Mulvany and Anne-Louise Sarks shift the focus from the adults to the doomed children playing upstairs, unaware of the tragedy soon to engulf them.

On the face of it this is a cheerier play than you might expect, full of cute, funny moments.

But it is underscored by a deep sense of foreboding, as the brothers unknowingly await their fate, making it somehow more unbearable.

For those who don't know, Euripides' tragedy sees Medea exact revenge on her unfaithful husband Jason (of the Argonauts fame) by killing his bride-to-be and then taking the lives of her own children.

All we see in this radical re-telling is the action taking place off-stage in the original play, with Medea herself making only the odd appearance.

Jasper and Leon are too busy playing soldiers and farting in each others' faces to get too caught up in what's going on outside, but their larks are permeated by a growing unease.

As you take your seat, carefully navigating a carpet strewn with foam bullets, cuddly toys and the prostate bodies of the two young protagonists, you're immediately plunged into protective parent mode.

When the lights go down, and the key turns in the door an overwhelming sense of claustrophobia descends as you feel yourself locked into the youngsters' fate.

Bobby Smalldridge, as Jasper, and Keir Edkins-O'Brien, as his elder brother Leon, throw themselves with abandon into the play fights.

But they also capture the subtle anxiety of siblings fearing the effect of family upheaval but too pumped up with bravado to confide openly in one another.

The script pulls off the fine balancing act of making the dialogue naturally childlike while offering an insight into these young minds.

At times, their infantile chatter has a disarmingly philosophical, almost poetic edge.

When discussing how long their parents' "marriage stuff" will take to resolve, for example, Jasper ponders: "So does it take longer if they do love each other or if they don't?"

Each time you fall under the spell of their childhood innocence, however, director Anne-Louise Sarks ensures you're jolted with another reminder of what is to come.

As they act out their fantasies of what a grown-up world holds for them, their breathless rush towards adulthood feels chokingly tragic.

Emma Beattie, in the title role, makes only a few fleeting appearances, but the emotional charge turns up a notch with every incursion.

It would be easy for her to become almost a pantomime figure, but it is clear this is a woman consumed with love for both her philandering husband and her children, without whom she cannot bear the thought of living.

As the young ones' lights are eventually snuffed out, the darkness is infused with the faint glow of the plastic stars stuck to their bedroom wall.

Horror is quickly replaced by an almost woozy sense that you're floating in some unreal half-world between innocence and brutal reality.

It's the children's naturalistic performances above all that make this such an arresting and refreshing take on a centuries old classic, and one which manages to be both funny and heart-wrenching.

Playing alongside children was 'lovely but terrifying'

Emma Beattie, who plays Medea, describes appearing alongside such young, precociously gifted actors as "lovely but a little terrifying".

"It's a lot rawer and a bit scarier because with adults you're used to analysing and rehearsing a play until you get to a point where you agree that's what works best," she says.

"These children live so much in the moment that the whole process is turned on its head. It's lovely but a little terrifying."

She has found herself reluctant to take to the stage at times so affected was she by the emotional intensity.

"Normally when you watch Medea it's possible to separate yourself a bit from the horror and think of it as something which is happening to other people," she says.

"But that's so much harder to do here because you fall in love with these children once you're invited into their world."

While this is a particularly extreme example of familial fall-out, the parallels with divorce and the strains it can have on children torn between warring parents are obvious.

"I spoke to a young chap after one show who told me it really brought home that moment his parents split up," says Beattie, whose own parents divorced when she was young.

"It's so easy for children to be caught in the middle and end up bruised and scarred because they're torn in their alliances."

* Medea is at the Gate Theate in Notting Hill until November 28. For tickets, visit www.gatetheatre.co.uk or call the box office on 020 7229 0706.