The critically acclaimed Peep Show is something of an underdog in the realm of British TV – a show that just doesn't know when to give up. After a strong first few series, it was almost cancelled amid a run of mediocre ratings – to the horror of the cult show's devoted fans. However, it was saved on the strength of this support and, in part, due to exceptionally strong DVD sales.

Now, though, it seems to be going from strength to strength: the sixth series has been commissioned even before the current fifth series has finished. Judging by what we've seen of the fifth series, though, they'll be no problem with maintaining the current standard of exceptional comedy.

We've seen the first four episodes of the fifth series and, when compared to the fourth season – which turned a bit too bizarre and slapstick for our liking – it's a vast improvement, returning to the cringe-worthy situations and embarrassing collection of social faux-pas that made Peep Show such a hit when it first debuted in 2003.

Part of the credit has to go to the writing team: Sam Bain and Jesse Armstrong clearly know their characters exceptionally well and, just as clearly, take plenty of guilty pleasure from placing them in a series of awkward situations.

Of course, crediting the writers with Peep Show's success risks doing a dis-service to the superb cast, not least leading men Robert Webb and David Mitchell. They've said in interviews that Peep Show could 'go on forever' and, when watching the show, it's difficult to remember that they've churned out a pretty rubbish BBC sketch show, for instance. They inhabit Mark and Jeremy with the ease that comes with playing a character for such a long time.

The supporting cast are pretty good, too, although the first four episodes of season five have seen them appearing less than we'd have liked. The flirtatious Big Suze, for instance – Jeremy's perennial old flame – only pops up in the first episode, and even more galling is the lack of Mark's boss, Johnson. He's one of the strongest characters in the show, and it's a shame that he only pops up briefly in two of the first four episodes.

The plot is, like previous series, on over-arching storyline that winds its way through each episode of the series, although it does take a somewhat meandering route when it gets in the way of some potential comedy. The main gist of the series is that, after leaving poor Sophie at the alter at the end of series four, Mark is living in a world of confused feelings and the potential trauma of having to return to work as a pariah.

This is manifested in different ways through the four episodes. The first uses the disastrous wedding as a mere springboard for Mark to pursue a hopeless relationship and the eventual burgling of his flat – watch out for the comedy, stereotypical chavs, who are hilarious. The second episode is a little better, as it keeps returning to the main story arc throughout – there's Sophie in tears, being comforted by villainous Jeff, and then Sophie being sick into a toilet. Honestly, it's better than it sounds. The third and fourth episodes, meanwhile, make mere passing references to what's gone before, which is a shame.

Of course, Peep Show wouldn't be complete with its trademark style of filming and direction. Few other mainstream sitcoms are as imaginative – or risky – when presenting the views of their characters, but Peep Show – the clue's in the name – hold nothing back. Almost all of the episodes are shown through the eyes of various characters, which is a system with numerous benefits. You can hear all of their thoughts, for instance, which are often totally different to what they've just said. It adds another dimension to the show and, for Peep Show at least, a vital one – it just wouldn't be the same without it.

There are a couple of niggling issues with the first four episodes of the series, but you shouldn't let them spoil your enjoyment of one of the finest British comedies to emerge since the turn of the Millennium. The reliance of Mark and Jeremy, above all else, does a disservice to a varied and excellent supporting cast who really need to appear more – only Superhans is the one who appears to buck the trend here.

There's also a bit less reliance on plot than in previous series, with Armstrong and Bain instead deciding to employ episode-specific story lines that, occasionally, feel like they're ignoring what's going on in the wider world of Mark and Jeremy. One episode, for instance, revolves almost entirely around the boy's flat being burgled. It provides for some brilliant comedy, sure, but you feel as if the rest of the show is being forgotten as the writing team pick up a potentially funny ball and run with it.

Despite this, it's a return to form from a series that, arguably, had shown signs of slipping. The last season had descended into a slightly ridiculous slap-stick affair but, thankfully, the embarrassing situations, dodgy one-liners and classic Peep Show comedy has returned. The series wraps up after the sixth episode airs at the end of this week, so catch it while you can – it's no wonder that a sixth series has already been commissioned by Channel 4.

[The preview disc we saw for review did not have the full collection of episodes or extras on it, hence we can't mark it at this stage]