David Walliams

There's nothing like a school trip to let the hair down and, as non-French speaking French teacher Miss Postern heads for France, with Mr Church chasing breathlessly behind - or chasing her behind breathlessly - this final romp with the staff and pupils of Greybridge School is a full-on ooh-la-la farce. David Walliams and Catherine Tate star in a comedy that makes Bad Education look the height of subtlety but a second term seems a certainty.

It's our last visit, for now, to hopeless Greybridge School as we eavesdrop on yet another of Mr Church's unimpressive chemistry experiments, conducted under the adoring gaze of moon-faced Pat (a silent Julie T Wallace).

But there's excitement on the horizon, at least for the staff, with a school trip to Dieppe, led by French teacher Miss Postern (Catherine Tate) who, oddly, has never been to France before. She doesn't seem able to speak much French, either, as her coachload of uproarious pupils and three male teachers arrive at their accommodation. What happens next is pure crude, rude and ribald French farce involving hotel corridors and gatecrashed bedrooms. And David Walliams has given himself a diarrhoea-related sub-plot that might make you feel queasy.

At last, the episode with David Walliams in his underpants - the comedy moment that's been trailed since this knockabout school comedy started its first term. There's a sporting theme as Miss Postern (Catherine Tate) sends rival admirers Mr Church and Mr Gunn into a testosterone-fuelled frenzy by donning a tracksuit for ironman triathlon training. They settle it the way men have done since the dawn of time - with a spot of wrestling.

Viewers have taken to Big School (co-written by David Walliams and the Dawson brothers) in droves and they are rewarded by plenty of these crowd-pleasing moments (come on, who doesn't want to watch Philip Glenister drag David Walliams from a set of wall-bars?). But the real scene-stealer is Steve Speirs (he was Ricky Gervais's unwanted "friend" in Extras) as sentimental, self-dramatising Welsh geography teacher Mr Barber. He's prepared his class for an important exam: "I'm looking for the geography teachers of tomorrow." Or so he thinks.

Meanwhile, Greybridge School is transfixed by rumours that the chemistry department's prissy deputy head Mr Church has slept with thick French teacher Miss Postern. The rumour was started by Cro-Magnon gym teacher Mr Gunn, Miss Postern's other suitor and Mr Church's rival. In a big slapstick set-piece Church and Gunn (Walliams and Glenister) wrestle - literally - for Miss Postern's affections.

A teacher's view on Big School

The staffroom stereotypes may be spot on, but even David Walliams can't save a show that laughs at teachers more than with them, says Sarah Jones.

Possibly thanks to its big-name cast - including David Walliams, Catherine Tate, Philip Glenister - Big School continues to have the feeling of a show that is a long way from being as funny as it should be. In fact, there's a rather unattractively retro, 1970s feel to tonight's episode, in which staff are instructed to behave sensitively towards a pupil called Josh: after an African holiday, his mum has run off with a Masai tribesman. Frances de la Tour as the headmistress remains the only bright spark in a class of underachievers.

Camp frolics on the couch are guaranteed as our host is joined by David Walliams for a triple-entendre gossip about sitcoms, Simon Cowell and whatever else crops up amid a bout of giddy tomfoolery. Keeping it a touch more real, Jamie Foxx and Channing Tatum will try to keep Carr focused on their new movie, White House Down, while music comes from Mutya Keisha Siobhan, once the original Sugababes. Who knows why their names aren't alphabetical - it's bound to cause trouble...

There's nothing subtle about Big School - for instance tonight's episode starts with a fart gag. But maybe that's why audiences enjoy David Walliams and the Dawson Brothers' cheerful, unsophisticated creation. Aged gags are telegraphed and thoroughly milked for every single comic possibility. Like the unfortunate pupil at Greybridge School, whose mother has run off with a Masai warrior during a family holiday. Cue sniggering staff making pointed and very lewd remarks (particularly grotesque headmistress Ms Baron) as thick Miss Postern ties herself in knots trying to be politically correct.

Elsewhere, Mrs Klebb presents the school play Juliet and Romeo, her "gender re-imagining of Shakespeare".

Who knew that gruff football gaffer Sam Allardyce was a fan of Strictly Come Dancing? When the West Ham manager reveals a weakness for the dancing show, fellow guest David Walliams takes him for a spin on the dance floor. The resulting intimate waltz is characteristic of the show: trying to hype up the macho banter but inevitably ending in back-slapping bawdiness. "I can see why they call him Big Sam!" Walliams coos.

In another playful TV rip-off, series regulars have their very own MasterChef challenge. Freddie Flintoff serves a surprisingly bistro-style fish and chips; Jamie Redknapp goes retro with a pineapple upside-down cake; host James Corden cooks an ambitious beef Wellington ("basically a big pasty," laughs Flintoff); and Jack Whitehall hacks at a pheasant carcass.

David Walliams to voice BGT dog Pudsey in movie

The 42-year-old BGT judge has signed up alongside owner Ashleigh Butler and Scottish actor John Sessions, who will play a baddie.