It's hundreds of years since native beavers last busied themselves on the UK's rivers and lakes. But they are at least getting people talking again now.

Next month, up to four beaver families will be released into the wild in Knapdale Forest, Mid-Argyll, meaning beavers will be free in Scotland for the first time in 400 years.

And earlier this month Natural England, the Government's ecological advisor, declared beavers could be reintroduced to England successfully, and might help restore and conserve rivers and flood plains.

But Natural England also admitted that the difficulties convincing landowners of beavers' benefits could mean it is many years before that day dawns; the Scottish beavers are in extremely remote country, but it still took a 10-year battle before the plan – over a set trial period – went ahead.

The fact that beavers have been reintroduced to most other European countries certainly doesn't wash with the Country Landowners' Association, which argues that: "We have a landscape unlike that of much of the rest of the world — one that has been actively farmed for hundreds of years. Our biggest concern is where the beaver would fit into today's modern, working English countryside."

You won't hear much of that kind of talk around the Lower Mill Estate's Flagham Fen wildlife reserve in the Cotswold Water Park, near Cirencester, where two pairs of beaver, each with an offspring of the opposite sex, were introduced in 2005.

They were put in a strongly fenced 50-acre enclosure, of which 37 acres are lake and the rest a mixture of woods and grassland.

That site proved to be too small a space for two families; an animal died, and one of the pairs was moved to a Devon reserve, one of just a handful of similar sites in this country.

But there has also been the triumph of three "kits" being born at Lower Mill, the first in Britain for centuries.

Dr Phoebe Carter, the biodiversity officer for both the estate and the water park, points out another way in which this site is nationally important.

"What's unique about what we're doing here is that we research the impact of beavers on the environment, working with the University of the West of England and Hartpury College," she says.

"They have already had a good impact on Flagham Fen. The trees they have felled have opened up glades in which new trees, flowering plants and shrubs can grow.

"Beavers are a 'keystone species'; they have a major effect on shaping their environment, which also affects many of the other species with which they share it.

"It is believed that they could create habitats suitable for up to 32 species in need of nature conservation action, including the threatened water vole, the otter and the great crested newt.

"Their feeding on the edge of the water creates ideal conditions in which coot and grebe can build their nests, and dragonflies and other insects benefit from the increased vegetation.

"We even have a heron here that uses the beavers' lodge as its roost!"

Dr Carter is well aware that it is not only the Country Landowners' Association that has its doubts about the reintroduction of the beaver, and she is keen to dispel them.

For instance, she swears, and we are inclined to agree with her, that the felled tree with which she is seen here is by no means as big as our photograph suggests.

Lower Mill, spread over some 540 acres and including seven lakes, is owned by the millionaire magazine publisher and property developer Jeremy Paxton.

He has put some spectacularly attractive and luxurious second homes on the site, but they and their grounds will account for no more than 100 acres.

The rest is being managed exclusively for nature conservation, and apart from beavers, there are also ventures to preserve and encourage bats, birds, insects, orchids and other rare plants, and mammals ranging from otter and water vole to roe and muntjac deer.

Like Dr Carter, Jeremy Paxton is keen to dispel fears about a species which, after all, not only fells trees to build its lodge home – blocking water to ensure that the entrance to it is under water – but sees the bark of willow and aspen as its core diet.

The crux of their argument is that Eurasian beavers are very different from their transatlantic cousins, which are much more sociable and gather to build very large lodge colonies.

"I think the people who are worrying have been watching too many cartoons," Mr Paxton says.

"The North American beaver is very different from the European beaver. These are non- destructive – they only do good for the environment.

Even in the tree-felling they do around the edge of the lake, they're not killing the tree, it's falling over, regenerating new growth and creating a nesting refuge."

The Cotswold Water Park Society is right behind him. "We acknowledge that there are some concerns, but believe that the net gain from having this species once again shape our environment would far outweigh any problems," it says.

"Experiences from European countries where beavers have been reintroduced suggest that most problems are minimal and easily prevented or resolved.

"The Netherlands is one of the most densely populated countries in the world, and there, beavers are celebrated as a symbol of natural restoration.

"In Bavaria, yearly damage caused by beavers is considerably less than daily damage caused by game species."

It is said that apart from Britain, the only country to which the beaver has not been reintroduced across most of its former geographic range is Liechtenstein.

The Scottish experiment next month will put an end to that statistic, but however well the trial reintroduction goes, we must not expect to see very much of these secretive creatures.

Although largely nocturnal, they do come out at dusk, or even during the day – but only if they are not aware of people around.

Beavers are Europe's biggest rodent, weighing anything from 33lb to 75lb, but spotting them will always be a rare treat, rather than a regular occurrence.

If they ever are released in England, we will know them by their habitat. The sight of a tall tree neatly gnawed to its knees by a handful of wild animals really is a culture shock in this country; and spears of shrubs and saplings stripped of bark are another sure sign you are in beaver territory.

Just how commonplace these sights will become in Middle England remains to be seen. But at the Cotswold Water Park, these fascinating creatures could not have a more persuasive group of people beavering away on their behalf.

return of the beaver

Beaver were hunted to extinction for their skins and meat, but most of all for their scent glands.

A traditional native mammal to Britain, it is thought to have survived in Wales until 1188, in Scotland until the 16th century and in remote parts of Yorkshire until the late 18th century.

Most valuable of all were their castoreum glands, which contain salicylic acid of the type used in aspirin because of the concentration of willow bark in the animal's diet.

Their medicinal qualities were well known by the Middle Ages. Indeed, Hippocrates knew all about them as long ago as 500BC.

The glands were known as beaver stones, and Dr Phoebe Carter believes that Beverston Castle in the Cotswolds, near Tetbury, which is still commonly spelled Beverstone, was built on the proceeds of trading in them.

Beaver fur was particularly in demand for making felt for hats, and there was also strong demand for the creature's prominent front teeth.

"In Lechlade in the East Cotswolds, burial sites from the sixth or seventh century revealed four women of wealth, each buried with a beaver tooth," she says.

"The belief was that they promoted healthy teeth in women, and were lucky charms for those expecting babies."