Outnumbered, BBC One

When it first aired in 2007, Outnumbered finally allowed viewers to see children on television really being children (hitting each other, lying, being naturally witty, shouting “Dad attacked that lady” in public), while ruthlessly exploiting the child’s unerring ability to say aloud what we’re really thinking, whether it's about terrorism (“What other religions have blown up planes, Mummy?”) or other cultural hot potatoes.

Written and directed by Andy Hamilton and Guy Jenkin, with the children improvising around the scripted adult actors, the show's main aim was to create a version of domestic life that was both instantly recognisable and amusing: an anti-My Family family, in other words. In this it has succeeded spectacularly. Unsentimental without lacking heart, charming without being too cute, true without being "gritty", above all it succeeds in being properly and consistently funny without seeming to try too hard, which isn’t something you can say about most British sitcoms. It has rightly picked up fistfuls of awards, and has just been sold to the States (though the odds on it surviving the transition in any recognisable state are slim).

We’re now on to series three, and life in the Brockman household is much as it ever was. Dad Pete (Hugh Dennis) is still a slightly put-upon history teacher, and mum Sue (Claire Skinner) is still a harassed hausfrau, and both are driven to distraction by the activities of their three children: 14-year-old Jake (Tyger Drew-Honey), nine-year-old Ben (Daniel Roche) and seven-year-old Karen (Ramona Marquez).

Last week’s opening episode was decidedly hit and miss, awkwardly introducing a new character in the form of Pete’s mum while the family characteristically unleashed seven shades of chaos on a tour of London’s historic sites. Last night they were all back on home turf, bouncing around the smart London end-terrace they can’t really afford. This was good news. Outnumbered works much better when everyone is getting on everyone else’s nerves within the claustrophobic confines of four walls, the festering resentments and petty feuds mounting up like a stack of red reminders.

Ben was showing unlikely potential as a chess grand master (with Darth Vader as second bishop) in between causing “friendly fire” incidents with the wine rack

As usual, last night nothing much happened and everything happened. Between mistaking Anusol for toothpaste and devising plans to put criminals in fridges, Karen was busy writing to Barack Obama about the nefarious sales techniques of Readers Digest, having being duped into believing the family had won half a million quid – “we could buy 500,000 Magnums” - and promptly telling everyone at school. Jake was in trouble for “receiving stolen breasts” online, a particularly tricky scenario as they happened to belong to one of his teachers; Ben was showing unlikely potential as a chess grand master (with Darth Vader as second bishop) in between causing “friendly fire” incidents with the wine rack.

Any action was peripheral to the tangled acts of human interaction. Like that elusive concept Real Life, Outnumbered tends to meander along of its own accord then bang! – something big, nasty and unavoidable crashes in and things bump up a notch or two, before they settle again. The parallel narrative in series two concerning Sue’s father, Frank, and his encroaching dementia was lightly worked into the action, unfolding convincingly and poignantly. The equivalent in series three, involving Pete’s guarded, humourless 68-year-old mum, battling a loveless marriage and a late-developing online poker addiction, so far seems forced and gratuitous.

It’s not the only nagging doubt creeping into proceedings. Outnumbered’s mix of naturalistic acting and unscripted improv is a tricky balancing act, and I wonder how much longer they can keep all the plates spinning. Three years is a mere wink of an eye in sitcom land, but it’s practically a geological era in the lives of child actors. In this series the kids seem to be caught in a kind of limbo. Drew-Honey is now demonstrably (over-) acting, while many of the gags last night were a little too self-aware and knowing: when Karen spoofed Piers Morgan (played, aptly, by a stuffed pink monkey) during an impromptu Britain’s Got Talent audition in her bedroom, she did so by saying that “this act symbolises everything that’s great about Britain”. It was funny, yes, but it suddenly sounded like an adult’s voice channelled through a young girl, when the true joy of Outnumbered has always been hearing children being funny without anyone pulling the strings.

Then again, perhaps these inevitable developments actually preserve the wider authenticity of the show. We watch Outnumbered because we want to recognise ourselves and our children, and an integral part of parenthood, after all, is the gradual process of lamenting our offspring’s perceived loss of innocence, their suddenly mannered behaviour, their precocity and self-consciousness. The show still resonates, just differently, somehow. More importantly, it still doesn’t push too hard, doesn’t drown its many finely drawn moments with a clunky laugh track, and still packs in more laughs-per-minute than any other recent Brit-com I can think of.

Sit back, enjoy, and then watch the Americans murder it.

• Watch Outnumbered on BBCiPlayer
• Find Outnumbered on Amazon