The Loch Ness monster is passe. Forget it. The one that's truly in vogue now is the Congo monster. Its official name is the mokele-mbembe. But it is, in effect, a Congolese Nessie. And a bunch of Brits - with a like-minded international crowd - are determined to find it.

The unseen creature, supposed to resemble a brontosaurus, is said to be found in the depths of the Congo swamps.

Mokele-mbembes are said to skulk in the Congo - especially in the Likouala region in the north, a vast and scarcely charted area of the swamp. Locals are alleged to have seen them again and again over the years.

Once an African hunter called Nicolas Mondongo, 17, was standing beside the Likouala-aux Herbes river, when, according to a collection of cryptozoologica, How Dead are the Dinosaurs?: "Without warning, the waters parted and a hughe animal surfaced - beginning with an extremely long, slender neck and well-defined head, followed by a very bulky, elephantine body rising upon four massive legs, and finally revealing a lengthy, tapering tail".

Redmond O'Hanlon, author of Congo Journey, describes a fearsome trip into the deepest jungle in search of the mokele. Once he hears something that he thinks might be a giant mokele-mbembe, "hung with testicles the size of beer-barrels" - the noise turns out to come from a pari of owls. Another time, he asks one of his guides if he's actually seem a mokele-mbembe.

"What a stupid question", said Doubla, looking genuinely surprised, stopping with the water-bottle halfway to his lips. "Mokele-mbembe is not an animal like a gorilla or a python. It is an animal of mystery. It exists because we imagine it. Bo to see it - never. you don't see it."

Adam Davies, 30, an enthusiastic Cable & Wireless project manager in Wythenshawe, Manchester is determined to track down the mokele.

With him will be about a dozen other enthusiasts, including various cryptozoologists from Canada, Sweden, and elsewhere.

Their name makes them sound like animal-lovers on secret assignment for a spy agency, but cryptozoologists are a sort of virtual zoologist, seeking to pin down the alleged creatures that science cannot reach.

The mokele-mbembe is just one of a long list of mythical monsters, including the bigfoot - man-meets-bear-meets-ape -- a "hairy hominid" with an 18-inch foot and a lumbering gait that's been seen in Vermont, Idaho and (more startlingly) Malaysia.