I've caught up late with Plebs, Sam Leifer and Tom Basden's comedy about three also-rans in Ancient Rome, which turns out to be a likeable enough affair, though you never entirely feel that they get out of second gear when it comes to the writing.

I did laugh aloud when the lads' landlord indignantly accused them of "Thracism" for wanting to get rid of a Thracian tenant he'd foisted on them, but I think that was partly because the line was delivered by the wonderful Karl Theobald. Also effortlessly funny, even when saying nothing at all, is Ryan Sampson as Grumio the slave. Shades of Baldrick - the dimwit's dimwit.

As London's big moment looms ever closer, the Bafta-nominated Olympic-themed sitcom returns for a final run of three episodes. This curtain-raiser, entitled Catastrophisation, opens with 32 days to go until the Games. Newly divorced Head of Deliverance Ian Fletcher (the excellent Hugh Bonneville) chairs his usual succession of interminable meetings, rammed with well-observed management-speak: "going forward", "win-win", "no-brainer" and other such babble. Lord Coe's on the phone, flapping about transport. Boris is worried about bikes. Everyone's obsessed with "sustainable post-Games legacy". Translation: desperately trying to flog the stadium to anyone who fancies it. Meanwhile, a delegation of American officials arrives to check security arrangements. As usual, Jessica Hynes as clueless branding consultant Siobhan Sharpe and Karl Theobald as incompetent infrastructure guru Graham Hitchins steal most of the laughs. Twenty Twelve's subtly satirical style is much gentler than The Thick of It or Veep but it does share one quality with those shows: as you're chuckling, there's also a creeping sense that somewhere this is all actually happening.

The final episode of the Olympic-themed mockumentary is as clunky as the rest. The satire isn't sharp enough and the comedy feels forced. But it's not the fault of the actors: Jessica Hynes is on fine form as branding exec Siobhan, negotiating to cover Anish Kapoor's Orbit Tower with a special wrap sponsored by a condom company, but when the accompanying rap video goes viral on YouTube the team threatens to alienate every single Catholic competing country. Meanwhile, Karl Theobald delights as hapless Head of Infrastructure Graham, forced to re-design the Olympic Torch Relay route so that it goes beyond Surrey.

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?

It's a strange little thing this. Dan Antopolski and Karl Theobald star as Tony and Steve Angel, two Italian brothers who only speak with Italian accents at home and spend their working lives dealing with unusual pests, such as suicidal mice and angry squirrels. Quirky and slight.