A welcome return for the Bafta-winning sitcom set in a corporation's dingy computer department. This is the start of series four. Many would have wielded the axe after a patchy debut run. The show's stay of execution was largely down to affection for writer/director Graham Linehan - the man behind Father Ted and Black Books, Chris Morris collaborator and recipient of comedy's Ronnie Barker Award last year. His creation is now worthy of those credentials, going from strength to strength. Tonight's opening episode is entitled Jen the Fredo, after the weak Corleone brother in The Godfather, and is crammed with knowing nods to the revered Mafia movie. Desperate to escape IT, Jen (Katherine Parkinson) is made Entertainments Manager by unreconstructed boss Douglas (Matt Berry) - a man given to pronouncements such as, "I like my women how I like my toast. Hot and consumable with butter." Jen's new job means showing braying businessmen a good time - and a theatre trip to The Vagina Monologues isn't quite the ticket. Back in the bunker, geeky Moss (Richard Ayoade) is devising Dungeons & Dragons-style role-play games and heartbroken Roy (Chris O'Dowd) keeps weepily guzzling white wine at his desk. All these plot strands come together ingeniously. Most laughs come from Berry and Ayoade's more cartoonish characters, but Linehan isn't too proud to write in the odd pratfall and it's so well-acted, one scene is genuinely touching, despite its silliness.

The best theme tune on TV blasts us back into the basement of the Reynholm Industries tower for series four of the comedy they might have called Take Me to the Geek. Our favourite IT support team is out of sorts. Roy (Chris O'Dowd) is getting over a relationship break-up and gazing at photographs of himself with his former beloved - a waste of time, since he's electronically blotted her out of them all. Jen (Katherine Parkinson) has applied for the job of company ents officer, even though everyone tells her sternly, "It's not for you." And Moss (Richard Ayoade) is fine-tuning a role-play fantasy game that requires a 20-sided dice. It's good to have the trio back, even though tonight's episode doesn't show the series at its demented best: this is a sitcom that's lovable even when it isn't hilarious.

By now The IT Crowd, beginning its fourth series, has a cosy familiarity. The three main actors - four if you include Matt Berry's deranged chauvinist boss - inhabit their roles so completely that there is no longer any need for them to strain for laughs. That much you would expect from a long-running series. But even so, tonight's episode is exceptionally funny. Jen (Katherine Parkinson) has decided to apply for the job of Entertainment Officer, which involves showing sexually frustrated out-of-town businessmen the sleazier side of the capital. Only on this occasion, these honking refugees from a 1970s sitcom are sucked into a game of fantasy role-play organised by the über-geek Moss (Richard Ayoade). The moral? It's OK to get in touch with your inner nerd.

I haven't been a fan of The IT Crowd in the past, so either this funny opener to season four has climbed a couple of rungs up the comedy ladder or I was totally wrong.

The four leads all seem to tot­­ally inhabit their characters much more than they did when we last saw them 18 months ago and ­everything about it feels that much more relaxed.

A fifth series has already been commissioned which only makes sense - at only six episodes a piece, it would take four British series to make one full-length series in the US.

And that alone could be another reason why it has taken until now for this show to really bed in enough to regularly provide laughs.

Creator Graham Linehan has said he'll write the next series with a team rather than on his own, which should also keep the quality right up there.

Tonight Jen (Katherine Parkinson) has applied for the job of Entertainments Manager at Reynholm Industries, unaware that the role traditionally involves the messy business of procuring hookers for business clients. Happily, Moss (Richard Ayoade) and Roy (Chris O'Dowd) come to the rescue with some alternative amusements - and a sub-plot involving Roy's freshly broken heart that will have geeks sobbing on to their keyboards like babies.

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Another dollop of Sunday night whimsy as the hemophobic former surgeon (Martin Clunes) and his cluster of eccentric Cornish folk return for a fourth series. Life continues much the same in the tiny fishing village of Portwenn, with all the locals getting ever more odd. The aging local chemist Mrs Tishell (Selina Cadell) has developed nymphomaniac tendencies. Scatter-brained receptionist Pauline (Katherine Parkinson) is losing sleep because of her brother's snoring. Big Bert Large (Ian McNiece) is missing the spark of love in his life. And all of them, for some reason, think they'll get some sympathy from the world's least considerate GP. The truculent medic, meanwhile, is nursing his own wounds following the departure of his paramour, Louisa, and it's made him restless. When he hears a desirable consultant's post is opening in London, he thinks that finally he might be able to overcome the fear of blood that previously ruined his career. First though, he has to overcome the shock of meeting a snooty former fellow student at the hospital in Truro, surgeon Edith Montgomery (Lia Williams), who makes no bones whatsoever about letting him know how low she thinks he's fallen.

Returning for a third series, Graham Linehan's office-bound sitcom seems to have been given a much-needed reboot. The swipes of cruel humour have been toned down in favour of the flashes of absurdist comedy Linehan perfected in Father Ted and Black Books. It's a good move, enabling Linehan to make the most of his superb cast, including Chris O'Dowd, Katherine Parkinson, Matt Berry and Richard Ayoade.

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