If a bawdy comedy comes out of the states you can bet that Judd Apatow will have had his filthy paws on it in some way. But although his involvement is seemingly ubiquitous, these days it's mostly in a producing capacity.

Surprisingly, as far as directing is concerned, this is only his fourth feature as director in his entire career. Perhaps the main problem with Apatow, and by association this film, is that he's such a powerful player in Hollywood, it probably takes a brave person to say no to him. And as far as this project is concerned, someone should have been saying 'no' to him on a regular basis.

It's quite a big week for married couple Debbie (Leslie Mann) and Pete (Paul Rudd), with both of them celebrating milestones in their lives by turning the big Four O. Well, Pete's the one actually doing the celebrating as Debbie has convinced most people that she's still only thirty eight. A party is being thrown nonetheless, with a large number of family and friends invited to the house.

Obviously there's not much you can do with birthdays, but the timing for this big event in both their lives couldn't be worse.

Pete is running his own music label, but is currently not doing very well. He has British rocker Graham Parker (playing himself) on his books, and is hoping for big things. Unfortunately for Pete, the world just doesn't seem that fussed about this particular sixty-odd singer. With his business doing so badly, it looks like selling the family house could be a distinct possibility. It also doesn't help that his dad Larry (Albert Brooks) is constantly looking for hand-outs.

Debbie owns a fashion boutique that's actually doing pretty good business, considering. She soon learns however, that the books don't add up and that one of her staff members appears to have stolen thousands of dollars from her.

There are a number of struggles at home too, with their eldest daughter Sadie on the cusp of hitting womanhood, whilst struggling with an addiction to watch the entire run of Lost in less than five weeks. They seem to be experiencing problems in the bedroom too, which isn't helping any.

So for a period in both their lives that the pair should find themselves embracing, they currently have far too many obstacles in their way to enjoy it. It doesn't take them long to come face to face with the following realisation: this is 40.

Turning 40 is a piece of cake. Eating cake without cutlery is another story.

With this on-screen pairing of Mann and Rudd first appearing as these character's in Apatow's 2007 film Knocked Up, you can see the appeal of catching up with them now, at this pivotal point in both their lives. Unfortunately the result is more like running into a couple you'd really rather not see. Ever Again.

If Apatow had followed the rules of the average rom-com, it may have fared better. But in This is 40, he's mutated the genre into something else: the epic rom-com. With a running time just shy of the two a half hour mark, this is the Cleopatra of the rom-com world. And that's not a good thing.

Inside this dangerously obese, bloated torso is a trim comedy dying to come out. But Apatow feels the desire to stretch the initial premise into something completely unrecognisable. A large segment of the film focuses on Pete's music business and the promotion of Graham Parker. Why Apatow chose Parker is anyone's clue. Parker is hardly a name that well known in the UK, never mind globally, so why he would feature him in such a large part is a mystery. Actually, maybe not that much of a mystery; clearly Apatow is a fan, and just wanted him in his film, and no-one had the good sense to say no to him.

And because of the sheer length of the film's duration, it actually feels like we're living it in real time, with no end in sight. With so many unnecessary distractions, the film actually loses sight of what it's supposed to be. Although it feels almost wrong to say that Megan Fox's character is an unnecessary distraction, she is clearly used for nothing more than titillation – well, it certainly wouldn't be for her acting abilities. There is no point to Megan Fox...actually, that's all that's needed for that sentence.

It may have a great cast, including comedy queen du jour Lena Dunham, Chris O'Dowd, John Lithgow, Melissa McCarthy, Jason Segel and a delightful turn by Albert Brooks, but there are just far too many of them. And at times it feels that many of them are simply used to comic effect, in attempt to lift the film from the almost melodramatic depths that it finds itself often plummeting to.

Perhaps Apatow, possibly having a little mid-life crisis of his own, wanted to attempt something more ambitious. And it's certainly that. But with this fast-paced world we now all live where, let's face it, with the popularity of social networking, couples can start and end relationships during this film's vast running time, you don't want to feel yourself grow physically older while watching any film. And you'll most certainly do that watching This is 40.

If he has any sense, Apatow will release the 'Necessary Cut' version on DVD, where it will play out with laughs aplenty in no more than 90 minutes, as that's the film he should have released in the first place.

This is 40 does have some entertaining moments, but there's just far too much filler to really appreciate them. In that respect the film doesn't do itself, or turning forty, any favours.