STAFF at England's only wild beaver colony denied that a European beaver which has set up home on the River Thames, near Oxford, is a fugitive from their estate.

Experts say the mysterious arrival is from a new source of beavers, and not one of the six introduced three years ago to the Lower Mill Estate - a luxury waterside housing development in Gloucestershire.

Tony, Cherie, John, Pauline, Gordon and Sarah were the first of their species to be seen in Britain since Henry VII's reign when they came to the reserve in Cirencester.

Since that time, the creatures have produced the country's first baby beavers for 400 years.

Property tycoon Jeremy Paxton built a metre-high fence around the 14-acre site to keep the beavers inside, although two have since escaped and been recaptured.

The new beaver, which has been living for more than three months at a secret location near Oxford, has been identified by teeth-marks in trees. The estate says the rodent is not one of theirs but has offered its skills to help catch it.

Dr Simon Pickering, Cotswold Water Park director of conservation, said: "It's not from Lower Mill Estate as far as we're concerned. It has probably come from a zoo or a small private collection, but it's difficult to say.

"Two have escaped from Lower Mill in the past but we caught them straight away. When this one turned up the Environment Agency contacted us. We went to look and confirmed there was a beaver because of the classic signs, mainly trees recently being gnawed.

"They are very good engineers and wonderful builders, but the Thames was just a bit too big for one to build a dam.

"We are assisting to re-catch it - there is a bigger issue here because of the possibility of a re-introduction project in lowland England."

The Environment Agency said the location of the beaver's lodge was being kept secret to avoid it being disturbed or harmed.