Follow the sunken lane to the point where it ends abruptly at the cliff's edge and it's hard not to be overwhelmed by the pathos of the place. For this hamlet on the Suffolk coast, little more than a collection of flint cottages, was once the foremost town in East Anglia.In the Middle Ages, Dunwich boasted six churches, three chapels and as many monasteries. It was a thriving port and even had its own mint. But today, the landward fringes of the old settlement and the ruins of a single priory are all that remain, the harbour and most of the town having been consumed by the North Sea over several centuries.
Tradition has it that on a quiet night you can still hear church bells ringing beneath the cold grey swell. And gazing out from the overgrown cliff edge that was once a churchyard, it's easy to see how such a fanciful story arose.
But Dunwich has another tale to tell - a hard-edged story of the sea and its continuous interaction with the land. It's a never-ending story that is quite literally as old as the hills. But if anything, it is more relevant today than at any time in our history.
For not only do we, with all our expensive infrastructure, have more to lose from coastal erosion even than the prosperous burghers of Dunwich, but there is some evidence that the forces ranged against us are becoming more powerful by the year.
Climate change, whether part of a natural cycle or exacerbated by atmospheric pollution and the greenhouse effect, seems to be a fact of life. And that means raised sea levels as the polar ice melts, as well as an increase in the violence and frequency of storms.
In 1990, the Intergovernmental Panel on Climatic Change calculated that if the emission of greenhouse gases continued unabated, global temperatures would rise by 1o C by 2025 and 3o C by 2100, leading to a sea level rise of 20cm by 2030 and 65cm by 2100. And such a rise is bound to accelerate coastal erosion.
When the sea is higher in relation to the land, it stands to reason that cliffs and beaches are more susceptible to wave damage. And because storms result in more high-energy waves, a combination of raised sea levels and more storms is doubly bad news for coastal defences.
But while the basic force that causes beaches and cliffs to recede in the face of an advancing sea is the smashing and grinding effect of waves, the factors that bring about coastal erosion are many and subtle. For example, rainwater soaking down into cliffs can dissolve and weaken them internally, as can the presence of underground springs, and this makes it more likely that they will succumb to attack from waves.
It's because the processes are so complex that it is notoriously difficult to forecast patterns of erosion. And whenever we attempt to interfere in the natural interaction of land and sea, tipping the balance of forces in our favour, then predicting the likely outcomes can be well-nigh impossible.
In the past, protecting vulnerable sections of coastline from destruction and inundation was reckoned to be a simple, if expensive affair, and it was mostly dealt with locally. If the sea was trying to get in, then commonsense dictated that, in order to keep it out, all that was needed was a sufficiently strong bank or wall, built to the required height.
But experience has taught us that it is rarely that simple. For one thing, the sea has an awe-inspiring way of tossing the sturdiest steel and concrete defences to one side - witness the topsy-turvy fragments of so many blast-proof bunkers and other military installations littering the beaches of Europe half a century after the Second World War.
And then there's the irritating question of what happens further along the coast when one stretch has been fortified. For the knock-on effect of local sea defences can be dramatic - and embarrassing.
Unless the changing flow-patterns of water and sediment are predicted accurately - an almost impossible task given the vagaries of wind and storm - then the construction of a splendid array of groins and sea walls to protect Resort A could easily result in Resort B losing its sandy beach in the course of a single night.
Nor is there anything to prevent the sea dumping the sand it took from Resort B right across the entrance to the harbour at Port C. Indeed it was the sudden blocking of the harbour at Dunwich - an event that resulted in a drawn-out feud with a neighbouring port - that started the series of disasters which would lead to the town's disappearance.
It is this need for detail that has led a team of scientists at the University of Newcastle to use aerial photographs, satellite imaging and computer technology to pioneer new techniques for the eventual mapping of Britain's disappearing coastline.
Led by Dr Jon Mills, the researchers have been creating a 3D computer model of an eight mile stretch of coastline at Filey in North Yorkshire, where land has been disappearing at a rate of 25cm each year.
"The traditional techniques involve watching wooden posts falling into the sea to estimate how much the coast is eroding," Dr Mills explained. "What we're doing is using satellite technology, digital aerial photography and ground-based global positioning systems to build the most accurate model ever of coastal erosion."
The scientists will then compare their model with monthly satellite photographs provided by the European Space Agency in the hope of predicting when and where erosion will occur.
Not that this knowledge will necessarily lead to the construction of banks and walls as it might have done in the past. For our new awareness of the complexities of erosion systems, coming at a time when the balance of power appears to be changing, has led to a controversial new approach to the problem - the policy of planned retreat.
The debate about planned retreat came to a head in the tiny village of Birling Gap, which comprises half a dozen cottages perched above the English Channel not far from Beachy Head in Sussex. For millennia the waves have been eating away at the soft chalk at a rate of around 75cm annually in the past century. In a few years, therefore, it is certain that the last remaining buildings will be swallowed up unless major engineering works are put in place to keep the waves at bay.
While the owners of some of the cottages argued for work that would save their homes to go ahead immediately, the National Trust, which owned three of the cottages, opposed any such intervention.
The Trust was backed by English Nature, which is the Government's adviser on wildlife, as well as the Sussex Downs Conservation Board, and at a public inquiry held in the nearby village of Alfriston, these organisations argued the following case for planned retreat.
As climate change takes hold, they said, the sea in the English Channel could rise to 54cm above its present level by the 2080s. The rock barrier proposed by some residents would only work for a limited period, in which time, its presence was likely to cause problems further along the coast.
"We cannot hold back the sea in the longer term," said the National Trust's regional director Sue Forster. "Managing the impacts of the erosion is, therefore, the only realistic course of action."
And English Nature went further. Birling Gap, it said, is an important and interesting site precisely because of the way that land and sea interact at the shoreline, as well as for the habitats it offers and the species it shelters.
Those pressing for sea defences, however, argued that the refusal of planning permission for their barrier would be contrary to Articles 8 and 1 of the First Protocol of the European Convention on Human Rights, which relate to the right to respect for a person's private and family life, as well as protection of their home and their property.
But in the event, it was the scientists who won the day. The inspector ruled against sea defences, concluding that "refusal of planning permission for the proposed revetments would not directly affect the dwellings on the cliff top, or the lives of those who occupy them, since the effects on them would arise from the natural process of coastal erosion".
Interestingly, the Secretary of State disagreed with the inspector on the matter of human rights, and conceded that failure of the State to protect homes from environmental blight might indeed be contrary to Article 8.
However, both Article 8 and Article 1 were, he said, qualified rights which require a balance to be struck between the interests of the community and the individual's rights.
At Birling Gap at any rate, planned retreat won the day - a significant decision because it will almost certainly mean that at other sites around the coast, the sea will be allowed to have its way, even if it does mean the loss of homes and property.
And at other sites, notably in Norfolk when soft unstable cliffs are exposed to the full force of the North Sea, planned retreat is already a pressing issue. The Norfolk coast has always been notable for its natural dynamics. To the north, the sea has deposited great shingle spits and ridges, and these offer precarious protection to the salt marshes that have long made the area a magnet for birdwatchers. But to the east, beaches and dunes are often all that protect low-lying land from the sea.
And between the two, and stretching 21 miles from Kelling to Happisburgh (pronounced "Haze-brr"), is a line of soft cliffs comprising silts, sands, clays and gravels that were deposited by glaciers over the past two million years.
For the low lying areas, with their bungalows and caravans, the chief danger is one of flooding, especially when winter storms coincide with unusually high tides. This was tragically illustrated on the night of January 30, 1953 when hundreds of lives were lost and thousands of properties flooded in the east of England during the worst flood in living memory.
The line of cliffs, meanwhile, supports several established towns and villages, as well as one of the country's most important natural gas terminals at Bacton. And it is these cliffs that are being eroded at an alarming rate.
Since the 1953 floods, more than pound;1 billion has been spent on keeping the North Sea at bay, and another pound;200 million will be spent over the next decade. But in the light of the projected rise in sea levels, such works are now considered economically viable only if the benefits can be shown to be greater than the costs.
Last year, North Norfolk District Council put forward a detailed range of proposals for protecting the clifftop village of Happisburgh. But when autumn gales took another 12m (39 feet) of cliff and resulted in the demolition of half a dozen chalets, the reduction in overall property value was enough to tip the cost-benefit balance. Major engineering works were no longer considered worthwhile by Whitehall, and since then, there have been fears that the community will be abandoned to the waves while cash is diverted to more convincing causes elsewhere.
And time is fast running out for Happisburgh. Nobody can say for certain how quickly the village could disappear, but houses, a pub, a shop and a hotel all stand perilously close to the edge. And then there is St Mary's, the fine medieval parish church. Standing 33.5m (110ft) tall, the flint tower has for centuries been a famous navigation mark for sailors. That's why it was bombed in 1940, only to be repaired in the 1950s. But today St Mary's faces a even more powerful threat than bombs. For, as the Government's own estimates indicate, if nothing is done to prevent its approach, the sea could tear the building down in less than 20 years from now.
For those who have lived all their lives in the village, even to contemplate such destruction is an act of betrayal. But as the burghers of Dunwich learned to their cost, the land and the sea are old adversaries, locked in endless conflict, and we, more often than not, can do little but observe their battle - preferably from a safe distance.