Last updated at 16:43 17 October 2007

A British fish fan has taken delivery of the world's biggest koi carp - a 4ft monster that tips the scales at a staggering six-and-a-half-stone.

The mammoth fish - nicknamed the Big Girl - is the size of a 12-year-old child and three times larger than any other carp in the UK.

Enthusiast Geoff Lawton paid an undisclosed sum for the 17-year-old koi from a specialist breeder in Japan. But he has already put a £30,000 plus price tag on the 90lbs specimen.

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Geoff, of Melksham, Wiltshire, said: "We've got some really big fish here - 25, 26 lbs - but she is more than three times bigger than that.

"We know she's the largest coloured carp every exported out of Japan - where you find the largest ones - and there's certainly been nothing like her in Britain before.

"She's swimming around our show pool at the moment, and every time I look at her, I'm still gobsmacked."

Geoff, 54, who runs the family-owned Rainbow Koi shop, added: "I don't want to sell her at the moment, but I wouldn't take £20,000 for her, or even £30,000. She's a treasure."

Big Girl was yesterday settling into her new home, an 8ft-square show pool in the centre of Geoff's shop.

She is a kagoi carp, which have a orange or gold scales and can live for more than 40 years.

British Angler Graham Slaughter, 42, caught the world's then biggest carp - weighing a whopping 88.6lbs - in a lake in France earlier this year.

It was said to be the first ever captured carp to weigh more than 40 kilos.