David Mitchell (I)

Tucked in between Thursday night's line-up of swords, smut and sorcery in Krod Mandoon and the bizarre brilliance of Psychoville, David Mitchell and Robert Webb's clever, crafted sketches act as a bit of a palate cleanser - a brief return to a sane world we can vaguely recognise.

The sketches where they painstakingly point out the basic idiocy of other TV shows always hit the mark and Webb's shouty, swearing TV chef who says "balls" a lot is a highlight.

So is Mitchell as a soothsayer in ancient Pompeii. Midway through series three, their policy of spreading their comedy net far and wide means their material is still as fresh as ever - unlike many sketch shows that rely on trotting out the same characters and catchphrases week after week for easy laughs.

That said, their running parody of a 70s sitcom - Get Me Hennimore! is totally inspired silliness.

This week's targets for David Mitchell and Robert Webb's satire include a shouting TV chef and homeopathy - both almost too easy to make fun of, you might think, but they find clever new ways. Even if the idea of a Casualty-style drama set in homeopathic A & E department doesn't make you laugh ("His chakras are fading! We're gonna need more crystals!"), the doctors' after-work trip to the pub should. Mitchell is on romping form, as good playing a soothsayer in Pompeii or a man who doesn't understand what an X on the end of an email means. There are dud moments - a swinger sketch doesn't even nearly work - but four weeks in, their stock of sharp ideas doesn't look like running out.

The smutty, fitfully funny, schoolboy comedy moves over from E4 in the same week as series three of Skins, sparking inevitable discussion about which offers the more realistic depiction of teenage life.

But this makes about as much sense as asking which paints a more accurate picture of adult life: EastEnders or Emmerdale. Correct answer? Neither.

But as Will, Simon, Jay and Neil set off on a geography trip to Swanage, Dorset, it will prompt coach-scented memories for viewers. While Jay is convinced that there's a middle-aged woman in Swanage eagerly awaiting the arrival of a bus-load of hormonal adolescent boys, Simon Bird's character Will still comes off like David Mitchell's geekier, more annoying little brother - the kid who has yet to learn that Yoda impressions will never get the prettiest girl on the bus to fancy you. A boat-load of trouble awaits.

Very much a game of two halves this week. In the plus column: a cheeky vegetarian backlash, the tragically oblivious weatherman and a disco-dancing Mr Darcy. But the ace in the pack is a sublime demolition of spy-in-a-casino film cliches, which pits a Bond clone against a Blofeld type in a game not of roulette or poker, but of guess the weight of the cake. Robert Webb seems to have been made up to look like Damian Lewis, and David Mitchell like Lucius Malfoy from the Harry Potter films, but that just adds to the surreal fun. The show tails off rather meekly with a mixture of head-in-hands cringe and wasted-effort caper (no, not Sir Digby Chicken-Caesar again!). But the memory of the croupier raking mounds of fruitcake across the gaming table is hard to shake.

If you lasted through to the end of Krod Mandoon you would have reached That Mitchell and Webb Look, which, three series in, is doing something rare among sketch shows: improving. The first two series were patchy - I might have said "hit-and-miss" but last night's episode featured a sketch lampooning reviewers who say that. Well, anyway: its hit-rate's up. The main characteristic of the show's humour is nerdish pedantry. If something improbable happens in a sketch, the characters won't follow comic convention and go with the flow; instead, they'll draw attention to it.

In one sketch, a man, played by David Mitchell, was having visions of the television chef Gary Rhodes - played by Robert Webb with a foot-high quiff. "Is that what Gary Rhodes looks like?" said Mitchell's character uncertainly. "No," beamed the vision, "but this is the best version of me that your imagination could piece together."

Another thing they do well: the good old-fashioned "subverting expectations" gag. One sketch was about a pair of sleazy snooker pundits reflecting on their time in the game.

"It's been me life," began one. "I've been obsessed with it, me whole life."

Pause. "That and snooker..."

The duo know their critics well: 'If we didn't perversely include 50 per cent deliberately unamusing material,' says David Mitchell in a self-referential script meeting in tonight's episode, 'they'd have to think of something else to say.' Well, that's us told, then. Happily there are more hits than misses in this instalment.

360 Degrees: Mitchell and Webb

Comedy duo David Mitchell and Robert Webb started life on radio, so when BBC producers had to make a red-button package to accompany the new series of BBC2's That Mitchell and Webb Look/c], it made sense to mine their unused Radio 4 sketches.

The third series of That Mitchell and Webb Look revealed that David Mitchell and Robert Webb can flit more deftly than Matt Lucas between comedy series (Peep Show) and sketch show. The first of the sketches encapsulated Mitchell and Webb's grasp of comic brevity: it gently satirised the conventions of a Poirot mystery. As their unmasking approached, the killer suddenly acquired a villainous voice and cigarette holder. The duo also made a very funny joke out of that thing we do when looking around the house for something, patting both our pockets as we rock on our knees.

Best of all was a satire of The Apprentice, which had the duo as TV executives watching a tape of a show featuring a relatively meek CEO - a Sugar-lite - dismissing a contestant politely and apologetically. But it didn't quite work, the executives thought, and so rethought the concept. "We deliberately pick 16 idiots - real idiots, arseholes as well," one of the men said, "and then we watch them screw everything up." But honestly, who would want to watch that?

David Mitchell and Robert Webb are probably more famous for the work that they do apart than for their shows as a comedy duo, now that Mitchell is the brilliantly witty guest of choice for edgily satirical panel shows, and Webb became a YouTube darling with his winning turn on Let's Dance for Comic Relief. They are terrific in Peep Show, but That Mitchell and Webb Look just doesn't hit the mark, probably because it's not very funny. Don't get me wrong, there are a few mild chortles - I liked Webb's filthy Queen Victoria at a tree planting - but there's nothing here that will have anyone gasping for oxygen as they fall, laughing helplessly, from the sofa.

If Krod Mandoon had been written by the same small army of writers who came up with this, it'd be really on to a winner. Much has been said about the death of the sketch show, but this first episode of the boys' third series made me laugh out loud so many times I was unable to make proper notes. Their deconstruction of The Apprentice is absolutely spot on. And after Robert Webb wowed us with his Flashdance for Comic Relief, it's extraordinary to discover how perfectly suited he is to the role of Queen Victoria. A stand-out sketch involving the gift of a tree is pure, rude genius and allows David Mitchell as her Prime Minister (I'm guessing from the beard it's the Marquess of Salisbury) to go off on a rant that plays brilliantly to his pompous strengths. It could almost be Peep Show in Victorian dress. Now there's an idea...