ONE moment you are in the cool darkness of a grotto and the next blinking in the sunlight, entranced by the sight of a fern-fringed pool or sparkling fountain.

There is a distinct feel of mystery about the Dewstow grottoes over and above that which comes from being in this strange, semi-subterranean world.

There is mystery too, in why such a place was built and the mind of the man for whom it was created.

"In fact we know relatively little about Henry Oakley, the man who had the gardens and grottoes built by the famous James Pulham," says John Harris of Dewstow House near Caldicot in whose grounds the grottoes and gardens lie.

"He seems to have been something of a disciplinarian but the scale of the gardens and the imagination that has been put into their creation speaks of an imaginative and perhaps slightly reclusive person."

By the early to middle part of the 19th century Dewstow Farm was in the hands of Henry Oakley, a bark merchant whose business was at Rodney Parade in Newport.

Henry's increasing prosperity was reflected in the visual enhancement of the large farmhouse into the substantial building which today is Mr Harris's family home.

But if Henry Oakley senior was content to enjoy his increasing prosperity and cultivate his broadening green acres, it was for his son, Henry Roger Keen Oakley to take Dewstow to its next, and most glorious phase.

A director of the Great Western Railway when the railways were at their peak of profitability, his interests included the cultivation of ferns and tropical flowers.

Some time around 1890, Oakley approached James Pulham, landscape gardener to the Monarchy and leading gentry of the day, and commissioned a fantastical and elaborate system of interlinking grottoes surrounded by garden and water features which are now considered to be among the finest of Pulham's work to be found.

"Pulham even remembered to fake the stalactites a real cave would have," Mr Harris says.

After the First World War, the gardens went into decline. They remained in a neglected state for years, until the decision was taken to uncover the grottoes, remake the gardens and return the whole spectacle to something very near what Pulham had originally envisaged.

Mr Harris employed a gardener and support staff to recreate the landscape of a century ago.

"With the exception of a tropical house that still has to be completely excavated and renovated we are as sure as we can be that Pulham's original groundplan is once again uncovered," Mr Harris says, proudly. "Yet there is still a great deal of information about the garden and grottoes and the people connected with them that we do not know.

"I would like to know about the people connected with the house and garden over the years and to collect, if possible, photographic evidence." l More information on Dewstow Hidden Gardens and Grottoes, which are open to the public on Sundays, can be obtained on 01291 430444 during office hours or on www.dewstow.com