All Rob Brydon and Steve Coogan do in this series is tease each other over expensive lunches, bicker a bit and do silly voices. How hard can that be? But after a while you realise there's more to this banter than meets the eye. It's impossible to tell how much is improvised and how much scripted, but when they go off on one of their comic riffs, it hardly matters. Tonight's subjects under discussion include Abba song The Winner Takes It All, film roles they didn't get (or were cut out of) and Woody Allen versus Les Dawson.

We're almost at the end of this unique comedy creation, which serves up English countryside to the tune of top level bickering from Steve Coogan and Rob Brydon over a series of very expensive lunches.

Part of the fun is working out how much of their not very polite and utterly random dinner party conversations have been thought out in advance, and how much is just flowing off the top of their heads as the food gets shovelled in.

Tonight, in the Nidderdale Valley, they're riffing on an Abba song, the comparative merits of Les Dawson and Woody Allen, and they learn more about limestone than they could possibly ever want to. Yes, it's all very moreish.

After tonight's penultimate episode, devotees will have watched two and a half hours of the comedians Steve Coogan and Rob Brydon playing lightly fictionalised versions of their real selves as they joke their way around an uneventful culinary tour of the North. This may sound like TV's answer to a large dose of Tuinal, but somehow the two men have managed to create something that's genuinely funny. Tonight's instalment takes them to the Yorke Arms, Harrogate, and contains one of the most surreal Woody Allen impersonations you're ever likely to hear.

The Trip (BBC2) got a thumbs-down in its first week, with many unable to see the point of sending Steve Coogan and Rob Brydon up north to eat and drink themselves silly while trying to outdo one another with their impressions. Well . . . the point is that it's one of the funniest things on TV. Yes, it can get a bit too cute at times, but the blurring of real and scripted identities gives the comedy real edge. The highlight this week was Brydon asking Coogan how it felt to have a career in nosedive after massive success early on; Coogan's reply was that it was better than always having been a mediocrity. I'd say it took a lot of guts on both their parts to leave that in.

The Trip episode 4 review: Hipping Hall

I suspected that this week's outing might mark a change of pace for the series with the introduction of a photo shoot, and so it proved, as for the first time the tragedy inherent in the show outweighed the comedy.

The Trip 1.4 review

This is a strange show to review, as there are times when the repetition goes far beyond a joke. That said, The Trip still has a peculiar grip on my attention, as there are instances when the comedy and drama knit very well.

Steve Coogan, fretful, vain and self-absorbed, thinks he might have met the female photographer who has arrived to take his picture somewhere before. This kind of thing is always a worry to the comedian, who tells his agent, "They [people in general] remember meeting me, but I don't remember meeting them." It's another corking instalment of Michael Winterbottom's funny, acute improvised observation of the odd, frequently jagged friendship between Coogan and Rob Brydon, his travelling companion on a northern road trip reviewing restaurants. Brydon is the more appealing, doing impressions during a difficult dinner with a peevish Coogan, his agent and said photographer. There's a brittleness to the fictionalised (or is it?) Brydon/Coogan relationship that gives The Trip its delicious edge.

We'd like to apologise for ever being rude about Steve Coogan. This and his recent Partridge on t'net things have made us fall for him all over again.

Rob Brydon and Steve Coogan are comedians of sufficient calibre that this series, in which they play versions of themselves on a restaurant-reviewing tour of the Lake District, was always likely to be funny. Four episodes in, it is revealing depth too. They eat at Hipping Hall in Lancashire, where they are joined by Coogan's assistant Emma (Claire Keelan) and a Spanish photographer, Yolanda (Marta Barrio). Coogan and Brydon revive the battle of celebrity impressions they fought in the first episode, amid increasing sexual tensions. "Is there a condition in Spain of Autistic Impressionist?" Coogan asks Yolanda, of Brydon. Brydon responds by quoting Alan Partridge at Coogan. "I'd quote your own stuff back at you," replies Coogan. "But I can't remember any of it."

Six to watch: TV impressionists

Steve Coogan and Rob Brydon have turned impersonating stars into a competitive sport. Who can rival their vocal skills?