When London's countdown clock to the Olympics ­malfunctioned last week, it was an uncanny rerun of the first episode of this cruelly observed docu-spoof.

The second episode finds London's Olympic Deliverance committee stuck on a bus with a delegation from Brazil and things are still refusing to run like clockwork. They're heading for a meeting with Sebastian Coe at the Olympic Park - or then again, possibly not, thanks to the wonders of satnav and bus drivers with only the vaguest grasp of London geography.

Leading a brilliant cast is Hugh Bonneville as the ­ultra-calm Head Of ­Deliverance - a master at "managing expectations" and staying positive at all costs.

We're also loving Amelia Bullmore (Head of ­Sustainability), waffling ­meaninglessly about how "Sustainability is not legacy", as well as Jessica Hynes]s shinily robotic Head of Brand and Karl Theobald's panic-stricken Head of Infrastructure.

The narration by David Tennant is as warmly soothing as a foot rub and the job titles alone are enough to make you smile.

The only downside in this perfect comedy of cock-ups is the BBC has been accused of ripping off 1998 Australian ­mockumentary The Games, about inept officials ­planning for the Sydney Games.

The BBC strenuously denies it, but the producers of The Games claim to have had talks with the BBC's head of comedy about a British equivalent, and actually loaned the writer of this one a DVD of their own show. So has the Beeb been a very bad sport?

Comedy, music and good causes - it can only be the show that makes you laugh until you give.

Harry Hill, Steve Coogan, Jennifer Saunders, Joanna Lumley, Ant and Dec and Armstrong and Miller are all doing something funny for money this year, along with the casts of The Inbetweeners, Outnumbered and Miranda.

We can also look forward to a specially shot mini-episode of Doctor Who, and James Corden will be back with the third instalment of his iconic Smithy trilogy - calling in favours from some very big names in showbiz.

Corden will also be one fifth of Fake That - a tribute band which boasts the talents of David Walliams, Alan Carr, Catherine Tate and John Bishop.

Never fear, though, the real Take That will be performing too. In fact, the night's going to be awash with boy-bands, as JLS are in the studio and it's The Wanted's turn to do the official Comic Relief single, Gold Forever.

The music line-up also includes chart-busting Adele, Annie Lennox, Elbow and Gareth Malone, who will be trying to turn some TV chefs into a Comic Relief choir.

Your hosts through this comedy marathon will be Davina McCall, Jonathan Ross, Michael McIntyre, Graham Norton, Claudia Winkleman and Fearne Cotton.

There have been 12 Red Nose Days since 1988, helping to raise more than £500million to help needy people in the UK and abroad.

There'll also be films from David Tennant, Jack Dee, Ruth Jones and Comic Relief stalwart Lenny Henry, each providing frequent reminders of how your money can help change people's lives for the better.

Twenty Twelve is a timely satire following the travails of the fictional team behind the 2012 London Olympics. The mockumentary has been chronically overused of late, but Twenty Twelve can be forgiven, firstly because it works so well and secondly because writer/creator/ director John Morton pioneered the format with the brilliant People Like Us.

The show charts the many catastrophes, both large and small, that already beset the Olympic project long, long before any spike disturbs the asphalt or a javelin is hurled in anger.

Finding a sustainable use for a Tae Kwon Do stadium, sorting out traffic congestion, dealing with obstinate artists, channeling Boris Johnson's enthusiasm and launching a faltering countdown clock are amongst the challenges of episode one. In a delicious case of life imitating art, the actual 2012 countdown clock broke down on the day of its unveiling, shortly after the satire was broadcast.

Hugh Bonneville provides star power as project leader Ian, but every scene is shamelessly stolen by Jessica Hynes as ignorant, neurotic, gibberish-spouting public relations guru Siobhan. David Tennant, meanwhile, provides the straight-faced narration.

John Morton, writer/director behind People like Us and Broken News, has a potential hit on his hands with this timely, engaging docuspoof. Narrated by David Tennant, it charts the bungling activities of the Olympic Deliverance Commission, a small team led by Ian Fletcher (redoubtable Hugh Bonneville), whose task is to smooth the run-up to 2012. On this week's agenda: nominating national heroes to be torchbearers (so that's, erm, Alan Sugar, Bruce Forsyth, Gok Wan...) and repurposing the tae kwon do stadium after the Games.

Every character in the ODC team shows promise, with Jessica Hynes amusingly maddening as PR bod Siobhan Sharp, whose assertiveness is exceeded only by her ineptitude ("Matthew Pinsent? I don't even know who that is"). She ends up babbling at the Tate Modern launch of her pet project - a hideous, green clock that mystifyingly counts backwards from 2012 to today. Seb and Boris, of course, get frequent name-checks and at least one of them will show up later in the series. It's a runner.

Deliciously skewering everyone from marketing creatives and PRs to web designers, John Morton's mockumentary (narrated by David Tennant) about the "Olympic Deliverance" team preparing for 2012 appears both painful and probable. It is the characterisation that is so sharp and knowing, while the execution is all the better for its subtlety.

Heading the team is the exasperated Ian Fletcher (Hugh Bonneville), who frequently despairs in his hapless staff. Aside from the bluff Nick Jowett (Vincent Franklin), who is prone to uttering, "I don't care who you are. I'm sorry, I'm from Yorkshire and I'm not having it", Fletcher is painted as the only one with a glimmer of competence. An early crisis is that the 2012 countdown clock has been designed by a curmudgeonly British artist, who refuses to explain how it works, or admit that it is flawed. It was commissioned by Head of Brand, Siobhan Sharpe (Jessica Hynes), a firm believer in "adspeak", who is often framed as clueless. Her suggestions for national heroes to be Olympic torch-bearers include Bruce Forsyth and Gok Wan, and she confuses the Poet Laureate Carol Ann Duffy with the Welsh singer Duffy. Meanwhile, her colleague Kay Hope (Amelia Bullmore), Head of Sustainability, wonders if the taekwondo hall might make a good donkey sanctuary once the Games themselves are finished.

David Tennant in Uganda for Comic Relief

"When Comic Relief tells you your services are required, you take your malaria pills and get on with it."

David Tennant writes for Radio Times about the suffering he's witnessed in Uganda - and the joy Comic Relief donations have brought to children there.

Alan Carr is so keen-as-mustard, so effervescently eager-to-please, he has rushed out this New Year's Eve special two days early. And it's a classy edition to round off the series: Carr is joined by the brightest twinkling star of this year's Christmas television, David Tennant, who will be discussing his performance in his final episodes of Doctor Who, though no doubt remaining resolutely tight-lipped on the plot details. Davina McCall also drops by to discuss the last-ever Celebrity Big Brother (coming soon - be warned) and music comes from Spandau Ballet.

Catherine Tate's Nan, a ruthlessly truthful creation, is best taken short. Nan's Christmas Carol (BBC1, Friday), longer than usual and later than usual because of Nan's language, cast her as a combatative Scrooge making three ghosts and her deceased husband sorry they were born. Or died. The most eye- catching ghost was David Tennant, who bore a striking resemblance to Russell Brand.

A Christmas Carol has seen many film and TV incarnations over the years. But this is perhaps the most bizarre and clever of all a comic retelling with Catherine Tate's acid-tongued Nan as Scrooge.

The writers have taken some bleedin liberties with the original story (Tiny Tim is a dog and the ghost of Christmas Present wears skinny jeans) but its a laugh-fest from beginning to end.

The three ghosties are played by Ben Miller, Roger Lloyd Pack and an almost unrecognisable David Tennant, who all attempt to convince Nan to swap her miserly ways for some seasonal cheer.