The Second World War pilots finally meet their match when they eye up a couple of comely lady air force personnel. "You see her, clocking my unit and all this... These girls are class though, isn't it?" But after a ham-fisted approach, the boys are in for a surprise. It's the last episode in the series, so I'll be sorry to say goodbye to the pilots and to archly filthy Brabbins and Fyffe (imagine Flanders and Swann crossed with Russell Brand) who tonight try to prove what swingers they are by singing a song about being gay. As for the new characters... well, some of them work and some of them don't. Hapless, clumsy historian Dr Dennis Lincoln-Park is a small joy, but the patronising Dr Tia is just a twerp. But the Public Information Film spoofs have been fun. Tonight's will strike a chord in anyone whose childhood was tormented by dire warnings about the dangers of abandoned fridges.

The boys keep up the high quality level that has been typical of this series, with hapless historian Dennis Lincoln-Park becoming a firm favourite. It might be the same gag week in, week out, but that's the absolute beauty of it. Guaranteed to put a smile on your face at the end of the week.

The two jovial comedians continue their quest to be the new kings of sketch comedy with the fourth instalment in this series. Tonight's highlight is "Divorced Dad" insensitively telling his young son that the reason the girl his son likes hasn't replied to his text message is because she's "out of his league".

While not every sketch is a side-splitter, those that do make you laugh out loud tend to creep up behind you and catch you unawares. Take this week's "Origins". It starts slowly with a group of grunting cavemen cooking a mammoth and then suddenly spirals into some very cleverly observed silliness ridiculing dinner-party small talk. It's brilliant. The Victorian pianist sketch - in which Armstrong keeps breaking into inappropriate and raunchy pop songs that offend his genteel audience - is another sneaky one. Culture buff Dennis Lincoln-Park has another accident with an "absolutely priceless" relic. The fact that you know what's coming makes it even funnier. The Second World War pilots don't want to dig out of a PoW camp because "We can't do escaping, isn't it? Because I've got all my asthma and s*** and he's got issues round worms." And viewers called Fred or Mick might like to know that they get a special mention this week when Miller's character Tom does his stream of "variations on a name" routine.

It's gentle, it's cosy, it's very British, and above all, it's a sketch show that's funny. Hurrah for Armstrong and Miller!

Like musical jokes. Never, ever funny, agreed? And yet, the best sketch in The Armstrong and Miller Show (BBC1) is the one where Armstrong is tinkling away on the piano in an Edwardian drawing room. Then he suddenly and seamlessly segues from Vivaldi or whatever into Gay Bar by Electric Six. Which makes the ladies faint. Funny, eh? Comedy, it's a mystery. Or possibly just pot luck.

I can't shake off the sense that this show has switched onto cruise control. It's still funny and there are excellent moments, but they come as occasional flashes. There isn't the sense of one belter of a sketch following another. Focusing on the positives, this week we get an inspired 1960s-style safety film that offers a neat solution to the lack of seatbelts in the backs of cars. And there's a new character, too: champagne-quaffing royal correspondent Terry Devlin, who sits in a breakfast news studio with a sweater draped over his shoulders answering questions such as "What would be the prince's state of mind at this time?" with an expertise that turns out to be distinctly limited. Alexander Armstrong's posh/slightly camp Northern Irish accent (if I'm hearing it right) for the character is a tour de force. Elsewhere, the Spitfire pilots have discovered that there's a spy in the ranks ("The group captain's well vex"). And the businessman who strides through the office taking on-the-hoof briefings learns "Beetroot's making a comeback" and "Nobody misses Sodastream". Plus, look out for a cameo from Dermot Murnaghan.

Alexander Armstrong and Ben Miller's comedy sketch show features the sort of quotably amusing characters that made Little Britain such a success. The street-slang-talking Second World War pilots, in particular, may well be remembered in the same breath as Little Britain's entertainingly verbose Vicky Pollard or Catherine Tate's snappy "Am I bovvered?" schoolgirl in years to come. In tonight's episode, the pilots are aggrieved that one of their "homeboys" has been talking behind their backs ("Oh my days, that's like, er, so two-faced"). Other highlights include Divorced Dad giving his son some frank - and rather crude - sex advice, and Terry Devlin, the Ulsterman Royal Correspondent, talking about the intricacies of the Royal Family's lives.

Chalkie Von Schmidt? A spy?! Theres some awfully bad news for the RAF pilots this week in another bunch of very likeable sketches from Ben Miller and Alexander Armstrong. A great old running gag makes a welcome return and a new character is introduced.

Its a royal correspondent who knows absolutely nothing about what the royals might be doing, eating or thinking but is nevertheless very happy to appear on rolling news channels and speculate about what he doesnt know at great length. It would be nice to see the pair introduce even more new characters like this one to keep things fresh.

Jilted Jim (the loser dumped on his wedding day for the DJ) pops up again tonight and the happy honeymooners probably arent the only ones groaning now every time they see his face.

Other bright spots include a warning about the danger of wearing T-shirts with writing on them. Meanwhile, the Neanderthals name a baby and we're reminded what a very dangerous decade the 1970s must have been by way of another terrifying Safety First film.

Consistently funny if essentially conventional, Armstrong and Miller's sketch show goes back to the old Kenny Everett format of using a handful of recurring characters to tell the jokes. Best this week are the prehistoric couple embarking on a naming ceremony for their newborn, who ends up being called "Mmm": 14 years later, Mmm is a classic grumpy teen forever frustrated when anyone bites into a tasty bit of mammoth.