Primeval (ITV1); CSI: NY (five): All is not well in the natural world. Brad and Angelina are "totally gay", according to Abby.

She's worried because these lizards - who did you think she meant? - "should be mating by now" and they're as interested in each as viewers are in another series of that dreadful new Nicholas Lyndhurst comedy.

Lizards who aren't the best of mates are the least of Abby's problems, what with the time portal in the Forest of Dean providing a doorway for animals from prehistoric times to go walkies in the modern world.

I'll pause for a while to let that sink in. The premise of Primeval, ITV1's bid to woo the Saturday family audience, is as difficult to swallow as a witchety grub. But if you're willing to play along with the premise, this promises to be wildly improbable fun.

It's hardly original, borrowing bits and pieces from umpteen other things - not just Doctor Who, but Stargate, The Lost World and Walking With Dinosaurs, whose makers provide the special effects as prehistoric monsters invade the 21st Century.

I half expected Raquel Welch in a fur bikini to follow closely behind them. Instead we have Hannah Spearritt, the former member of S Club 7, who didn't have to do Big Brother to raise some cash. On second thoughts, the sight of housemate Jo, fag in one hand and mouthing nasty comments, would make any monster have second thoughts about passing through the time slip.

Hannah's Abby ("I'm a lizard girl, Tim") flounces around in small knickers, presumably to distract us from the holes in the plot which has Ben Miller, at his most pompously silly, as the civil servant charged with covering up these weapons of mass destruction from a bygone age.

He's not happy having to deal with an anomaly - the name top scientist Douglas Henshall applies to the time portal. "You spend your life planning for every crisis imaginable up to alien invasion and then this happens," moans Miller.

Lucy Brown is the Home Office official on the spot who, very public spiritedly, says: "I suppose I owe more to the taxpayers than sitting in my room drinking the minibar."

Henshall's determined to do a spot of time-travelling, as he's convinced his wife, who went missing in the Forest of Dean years ago, is on the other side after he finds her camera during a trip back in time.

Her photographs, when developed, look like holiday snaps. There she is in prehistoric times and the picture shows her striking Page 3 girl poses. Surely she should have pointed the lens at the menagerie of prehistoric creatures around her?

"Believe me, it's far from over," Henshall assures his team after they've seen off a particularly fearsome creature. How right he is, there are five more episodes to go.

The forensic team in CSI: NY were dealing with something nasty too - a mummified body. "Dehydrated flesh takes some getting used to," admitted Dr Driscoll, carving the corpse like it was the Sunday joint.

More alarming was the sight of three women, dressed identically as Audrey Hepburn's Holly Golightly character in Breakfast At Tiffany's, walking into a jewellery store at the start of the programme.

They looked like they'd slipped through a time portal - and the sawn-off shotguns they pulled from I LOVE NY carrier bags confirmed they were as dangerous as any T-Rex.