Steeped in history, full of beautiful flowers and shrubs, and with a myriad mysterious tunnels – Mervyn Hancock visits Dewstow Gardens

YOU think you've just about got your own modest plot in order, and then someone sends you along to look at one of the most beautiful gardens in Britain. The result is amazement, envy, and the desire to go back again and again.

And once you have seen Dewstow Gardens in South Wales, you really will add it to your list of places to take visitors and friends, and wonder at the sheer hard work and loving care that has gone in to it.

Tucked away in the quiet village of Caerwent, not far from Chepstow, in Monmouthshire, is the Dewstow Golf Club, owned and run by the Harris family, who used to farm this land – until they made a remarkable discovery.

When “Squire” Henry Oakley turned his hobby of cultivating ferns and tropical plants into an obsession, he created what locals called “a wondrous and magical place” on his newly acquired Dewstow Estate – “the like of which is not known to exist anywhere else”.

At the end of the old millennium there was just a vast overgrown area which had been left to the elements and the grazing livestock. But initial clearing started to reveal lots of interesting rock formations and pathways.

In fact, this was a lost garden with tunnels and underground grottoes buried under thousands of tons of soil for more than 50 years.

Henry didn't encourage too many guests and the gardens were not widely known about at the time.

Then, when they were taken over after his death, the purchaser decided that he wanted nothing to do with rock gardens and sunken grottoes, and levelled the whole thing off by tipping hundreds of tons of topsoil over the area in order to make more grazing land for his cows.

The beautiful gardens – built in about 1895 and the squire's pride and joy – were buried just after the World War II and would have to wait half a century to be rediscovered in 2000.

Indeed, many years after old Henry – a former director of the Great Western Railway, whose other love was the breeding of shire horses – had departed, the estate was sold again to new owners who began excavating, and suddenly became aware that they were uncovering a treasure trove.

It all happened by sheer accident when Elwyn Harris, and his two sons, Mark and John, started to examine their new property in greater detail, and noticed something rather strange in the garden and grounds. There were pieces of rock projecting from parts of the soil – some close to the house, and some further away, towards the road.

At first they thought it was a natural fault in the ground strata, or that they had stumbled across some major archaeological discovery.

But they realised it was neither of these, because some of the rocks had their corners chipped off, and, beneath the natural-looking surface, there appeared to be bricks.

The seven acres of gardens had been buried in about the 1940s and Fifties and after excavation, although some areas were in very poor condition, other parts remained as good as the day the gardens were built.

Most of the repairs have now been completed during a restoration operation which began in 2000.

The gardens contain many ponds and rills, and interestingly, a labyrinth of underground grottoes, tunnels and sunken ferneries.

The rock gardens, ponds, water features, ornamental areas, tropical glasshouses and an enormous collection of plants, shrubs and trees from around the world must have delighted Henry's few friends and visitors, but as they stood back in sheer delight and amazement, they had literally scratched the surface.

The Harrises uncovered a piece of paradise – like the rock garden, which emerged from beneath an old orchard and concrete farmyard.

And not just any old rock garden – these had been created by James Pulham and Son, eminent landscape gardeners of the 19th and early 20th centuries, and most widely remembered for the spectacular rock gardens they created in many country estates around the United Kingdom, including the royal estates at Sandringham and Buckingham Palace, and the RHS Gardens at Wisley.

The ponds were almost intact, with most of the large natural rocks still around the edges, and the excavators could see where the original paths had been laid, although the beds had to be arranged and planted.Pergolas were erected over the original tunnel openings, which people viewed from above as empty holes.

Over the years, most of the surface gardens were filled in at various points, but the excavation has shown that what has been uncovered so far is in excellent condition.

Unfortunately, the glasshouses have long gone, as have the ornaments and many special features around the gardens – either broken up or sold by previous owners. But it is fortunate that the Harris family realised that they had bought into a slice of English and Welsh heritage, and decided to do something about it.

They decided to appoint a head gardener, with special responsibilities for planting the restored garden, and now, after eight years' hard work, they have fulfilled their dream – the underground network is now opened up and, but for a few repairs, is back to its former glory.

The gardens are open from 10am-4pm on certain days. Tickets: children £3.50; adults £6; concessions available. For more information, call 01291 430444.