The white cliffs of the Seven Sisters and Beachy Head are one of England's great iconic landscapes.

Scratch at any image of England and the strip of chalk cliffs between the Downs and the sea is never far below the surface.

The arts and crafts movement of the early 20th Century idealised the Downs. It was not by chance that Second World War propaganda used paintings of the Birling Gap with the slogan: "Your Britain. Fight for it now".

Photographs taken at the beginning of the century show the cliff top at the Birling Gap 60 or so metres further out to sea than today.

Sixty or so metres from a row of cottages that are today at the centre of one of the bitterest planning battles in Sussex. The battle to build sea defences and try and stop the erosion at one of only six beaches on England's south coast untouched by man.

The Birling Gap's landlord, the National Trust, backed by a clutch of environmental organisations, want the cliffs left to erode naturally - something they are doing at rate of about three-quarters-of-a-metre every year.

The owners of three of the six cottages, backed by the Birling Gap Cliff Protection Association, want to build a sea wall to stop the cliffs crumbling back any further and the homes falling into the sea. Sea defences seemed to have won last year when Wealden councillors, against the advice of their own officers, backed the smaller of two plans for a rock wall at the base of the cliffs.

Such is the sensitivity of building a sea wall along the iconic coast that Deputy Prime Minister John Prescott was quick to call a public inquiry into the scheme.

Such is the sensitivity of telling householders to leave and watch their homes tumble into the sea, the National Trust last week offered to buy the three homes it does not own.

The trust is scathing about the proposed sea wall, saying it would damage the cliffs, it would not work and would cause further erosion elsewhere along the coast - a process likely to speed-up as sea levels rise.

Caroline Richardson, the trust's managing agent at Birling Gap, says: "The proposals would not be effective in achieving the goals they set out to achieve.

"The best it would do is to provide a few more years life to some of the cottages."

The trust demolished one of the cottages in 1996 and owns three of the remaining six as well as the Birling Gap Hotel. Of the three privately-owned cottages, one is someone's main home. The others are holiday or second homes.

One of the owners lives in a care home, another died at the end of last year. The third cottage belongs to Jean Fawbert and turning her out of her home is the touchstone of this 21st Century battle.

Alan Edgar, of the Birling Gap Cliff Protection Association, is equally scathing about the trust, saying: "It is a body living in the past and trying to implement feudal policies.

"They have colluded and connived to gang up on the owner-occupiers at the Birling Gap."

He says the trust has a legal and moral responsibility to protect the cottages, while the sea wall itself would only be visible if parts of the cliff were washed away. Against him are environmental oganisations such as English Nature, the Countryside Agency and the Sussex Downs Conservation Board. They argue either of the two proposed sea walls, one 30 metres long, the other 200 metres long, would create an artificial promontory with the cliffs being eroded at either end.

The cliffs are the finest remaining example of a glacial dry valley in England and have been protected as a site of special scientific interest since 1953. It is the longest natural exposure of chalk cliffs in Europe.

It is on a heritage coast, butts on to a voluntary marine conservation area and is inside the Sussex Downs area of outstanding natural beauty. The area's coastal management plan, drawn-up by local authorities and the Environment Agency, recommends there should be no defences.

For English Nature the geological issue alone makes it important sea defences are not built along a "critical part of our national heritage". Richard Leafe, of English Nature, asks: "What makes Birling Gap special? Is it the cottages or is it the coastline?

"We believe the Birling Gap needs saving and the way to save it is to allow it to erode naturally as it does now. We are not trying to demolish the houses, we are suggesting things continue the way they are, the way they have been and the community has lived with for many years."