Man Down (C4), the sitcom starring and written by Greg Davies, is steeped in the history of TV comedy.

The trouble is, it tries to pay homage to every genre -- and the result is a slapdash jumble that can't decide where to earn its laughs.

Greg plays a useless slob of an ex-teacher called Dan, a 50-year-old who lives like a drunken student. It's a tribute to The Young Ones: in the first series, Rik Mayall played his dad.

But some of the jokes belong in Terry And June. Surveying the residents of his mother's retirement home, Dan sighed: 'They all moan about Marks & Spencer, but they won't buy their blouses anywhere else.'

Sometimes, Greg tries to ape Tony Hancock in his writing. One line, about having 'callouses the size of marrowfat peas', was a deliberate echo of Hancock's classic complaint: 'I've got toes like globe artichokes!'

Man Down needs to decide what sort of sitcom it really is. In fact, it needs to grow up a bit.

There is no trouble in Man Down (Channel 4), which is on series four already and still packing in the gags and the grotesques. Like Bounty Hunters, this sitcom is built around the comic persona of its creator-star, sarcastic ex-teacher Greg Davies. Only this man is kept down not merely by his own nincompoopery, but by the collective efforts of a support cast.

This episode features a cameo from Trevor Nelson; the woman in the cafe using a fry-up to educate Dan on the horrors of childbirth (harrowing yet unerringly accurate); and Mr Crumbs, a dungarees-clad giant who lives in lost property storage. As Jo says to a horrified Brian, by way of introduction: "He's one of my best friends! He once held his breath for an hour!" All these characters, however incidental, are fully realised and often gifted with the best (read: filthiest) lines.

The fourth season of a sitcom that's more likely than any other current show to provoke proper, hooting, tearful mirth. Greg Davies and his collaborators have an infectious love of imaginative profanity (this week, Stephanie Cole rolls out the phrase "venison bukkake" with some relish) and a delight in methodically creating big visual payoffs: the way two subplots conspire to produce a single glorious shot of Davies looking particularly absurd is a work of comedy art.

Man Down, Channel 4, review: "Surrealist fun"

Comedian Greg Davies may have got a much later career start than Jack Whitehall but like him, seems to be making the most of his moment in the sun playing over-the-top idiots, although his are rather lower down the social scale.