Once upon a time, before she became a comedian, Jo Brand was a psychiatric nurse. Now she stars as a nurse in an old people's ward in Getting On, a comedy with a resolutely dark heart. It was directed by Peter Capaldi and the hand-held camera, jitteringly close to the action and people's responses, reinforced the same uneasy, quease-making intimacy the technique also gave to The Thick of It, in which Capaldi played the foul-mouthed spin chief Malcolm Tucker.

Just as The Thick of It exposed political corruption, Getting On revealed the daily reality of cutbacks and petty bureaucracy now blighting the NHS. A turd sat on a chair for almost the entire duration of the show, first because a specialist turd-removing medi-testing outsourced company needed to clear it, and only then because the turd was being used as part of a vital research exercise to secure funding for the hospital. The staff struggled and failed to understand a woman speaking in a foreign accent. There were piercing notes to the character portraits: the ward sister was neurotic and ineffectual but also heartbroken. For all her dead-eyed scorn of her seniors, Brand seemed nice about the patients, until she ate the cake belonging to one dead old woman. She also lifted her family pack of Starburst.

One of the clues to successfully turning an in-joke into an out-joke is to trust people to get it without too much signalling. Getting On, a comedy set in an under-resourced geriatric ward, clearly understands this, beginning in a way so indifferent to the arrival of newcomers (us, watching) that you almost feel you should cough to let them know you're there.

Sister Flixter is sitting by an old lady's bedside, one hand checking her texts, the other clasping the patient's limp hand. The camera pans slowly to show a cake - "Happy Birthday Lily 87" - and then, without any fuss, it becomes apparent that Lily isn't going to be eating any of it. It's the kind of detail that might be played for cheap pathos in a different kind of series, but here - without a line of script - it very effectively delivers a key signature. This is a comedy about a place where the bleakly mortal and the banal are continually rubbing up against each other.

Sister Flixter didn't have much time to worry about Lily because a something distracted her, a coil of excrement discovered on a ward chair by Nurse Wilde (Jo Brand). To Nurse Brand, this is "shit". To Sister Flixter, it's a "critical incident", which will require the requisite NHS paperwork and to Dr Moore (Vicki Pepperdine), it is a "faecal deposit" and valuable raw material for her current research. For want of a stool pot the stained chair was pushed into an alcove behind hazard tape, where it is still odorously contributing to the ward's atmosphere of mismanagement when the new matron turned up later to add yet another chief to a tribe already short on Indians. That's the central joke of Getting On - of priorities and interests competing so effectively that virtually nothing gets done - though "joke" is too crude a word for the stealthy way in which the humour bubbles up through the cracks.

Written by its three leads and directed by Peter Capaldi, Getting On is in the tradition of The Office and The Thick of It, rather than Only When I Laugh or Green Wing. You can feel the grit of real events inside the comedy, such as the ludicrous attempt to translate the genial babblings of a patient speaking some unidentified Indian language (they discover she's been saying "I want to die. Please kill me") or the closing moment when Sister Flixter and Nurse Wilde found themselves having to mumble their condolences to Lily's sister, through mouths still filled with the dead woman's cake. And the most surreal gags turn out to be true. Dr Moore's strange obsession with the patient's bowel movements turns out to be the result of an ambition to "expand the Bristol Stool Chart from the current seven to an exhaustive 37 types of patient faeces". Wonderfully, the Bristol Stool Chart really does exist, a turd-spotter's identification chart that runs the fecal gamut from "hard lumps, like nuts" to "entirely liquid". Getting On doesn't feature on it anywhere.

The opening line of a comedy is crucial in setting the tone - it lets you know where the writers are coming from. So when Getting On dumped "there's a s*** on the chair" on us as an introductory gambit, it was clear this wasn't going to be an easy ride. That the words were squeezed from the lugubrious gob of Jo Brand, resplendent in nurse's uniform, only piled on the agony.

Yet I can't remember the last time I howled so loudly. Cut from the same downbeat naturalistic cloth as The Royle Family and The Office, Getting On mines the misery of a hospital geriatric ward for bleak laughs. Yet for all its pot-shotting at NHS bureaucracy and patronising consultants, there's a heartening thread of humanity that stitches this mordant little gem together.

You don't need to have spent any time in geriatric wards to get Getting On but possibly it helps. Director Peter Capaldi (taking time out from political jiggery pokery in Torchwood and The Thick Of It) gets the feel of washed-out light and weary resignation spot on; even the corridors feel like they're shrugging their shoulders and doing all they can to keep from falling over.

But where Getting On really scores is with the performances of its central trio of writer/actors. Brand is matched every cynical sigh of the way by Joanna Scanlan and Vicki Pepperdine as the lap dancer-booted sister and the stool-obsessed consultant ('what type is it?' 'I'd say type four: snake') around whom Getting On revolves in increasingly desperate circles. One heartbreaking, hilarious scene summed up. An Asian woman had been muttering away in her bed for an age and finally the nurses got a translation over the phone. 'What's she saying?' 'I want to die, please kill me.' 'Put it in her notes.'

The New Statesman Review

It made me laugh out loud twice, which is more than can be said for virtually all the new comedy I've seen in two years.

There are some real loud laughs to be had from Getting On, but they aren't comfortable, as this is a black, black comedy set in one of the more decrepit outposts of the NHS. Co-writers and stars Jo Brand, Joanna Scanlan and Vicki Pepperdine are the hopelessly incompetent staff of a pitiful geriatric ward. Brand and Scanlan are nurses rendered almost immobile by their own indolence and stupidity, while Pepperdine is a doctor who can't see her way past politically correct, coy euphemisms, as in "the deceased party" for "dead woman".

Getting On bears the fingerprints of The Thick of It, and not just because Peter Capaldi directs. It has the same ruthlessly naturalistic, documentary feel as its mighty predecessor and leaves the same lingering feeling that beneath the humour there's something very serious going on.

This is followed by Jo Brand's superb new comedy, Getting On. Set in the geriatric ward of an NHS hospital, it is centred around four brilliantly observed members of staff - a nurse newly returned to the NHS (Jo Brand), a subtly insane nursing sister (Joanna Scanlan), a male matron (Ricky Grover) and a brittle doctor (Vicki Pepperdine). Directed by Peter Capaldi, it is filmed in the verité style of The Office and The Thick of It using shaky cameras and dialogue that sounds overheard rather than scripted. It was the wonderful surprise of the week.

Here's something to savour from writer/stars Joanna Scanlan, Vicki Pepperdine, Jo Brand and director Peter Capaldi (The Thick Of It) - an extraordinarily funny, jet-black three-part sitcom set in a miserable NHS geriatric ward where the nurses are hopelessly bounded by bureaucracy and political correctness. Frighteningly familiar at times - which is surely partly down to the fact Brand used to be a nurse herself before she launched into stand-up.

Peter Capaldi has made virtually no mistakes since Local Hero. His is a CV that screams 'class' louder than someone at a pub quiz tiebreak asked to name Andrew McCarthy's debut film. So it's no surprise that when he turned his hand to directing a sitcom, it's extremely well made. Jo Brand and two less well known actresses play nurses on a medical ward that's overloaded with OAPs. They have to deal with NHS bureacracy which requires them to fill in forms and file faecal matter. It's a cynical, dry and washed through with realism. It is a lot like The Thick Of It, but understandably, and that's not a bad thing.

Dr Pippa Moore's Casebook

Ahead of the first episode, Doctor Pippa Moore gives us an insight into her daily routine...

You really shouldn't laugh. That's what you'll keep telling yourself during the first episode of this dazzlingly low-key new comedy set in a geriatric ward.

But it's no good putting on your politically correct face and sitting there tutting, because this is a relentlessly funny, workplace comedy that is right up there with The Thick Of It or The Office.

Part of the BBC's coyly titled Grey Expectations strand about the joys of ageing, the morbid humour is as black as death itself. Produced on a budget that would barely cover hair and make-up on Ugly Betty, it's written by Jo Brand, Joanna Scanlan and Vicki Pepperdine who also star as the self-interested, bored and incompetent medical staff. To add to its credentials, it's directed by Peter Capaldi, most famous of course as The Thick Of It's explosive spin doctor Malcolm Tucker.

Brand, as everyone knows, used to be a nurse in a psychiatric hospital which must surely account for the way that every horrible detail is so ruthlessly observed. You feel you could be watching a documentary filmed by an undercover C4 researcher with a camera hidden in a bed pan.

As the patronising, brisk, and utterly ineffectual Dr Pippa Moore (obsessed tonight with a poo that has been left on a chair), Pepperdine is absolutely spot-on and instantly recognisable, while the team's joint dealings with a patient who speaks no English are toe-curlingly sublime.

But just remember, you really shouldn't laugh.