Leading lights of the underground: Two artists are planning to convert a subterranean water-tank into an environmentally friendly Gothic palace, complete with mosaic floors and a secret passage

FOR SALE: three-bedroom family home, wonderful views, but no windows. Secluded

location, 12ft underground in a field . . .

For pounds 5,000, Jonathan Rodney-Jones and Shannon Ridd believe they got a bargain, but their wisdom was questioned five years ago when they bought a disused water-tank near Braunton, north Devon.

Everyone told them that they would be refused planning permission because it was on undeveloped agricultural land. But earlier this month they were given approval to turn it into a home.

It will not be a conventional structure. Mr Rodney-Jones, 28, and Ms Ridd, 27, both artists, intend to build a subterranean, environmentally friendly Gothic palace, with underlit mosaic floors, stained-glass walls, a stage and a secret passage. The home will fit into the 32ft by 60ft brick tank, which is believed to have been built in 1904 and was in use until the early Fifties. It was sold by the South West Water Authority before privatisation.

Access is via a mud track and the only neighbours graze in the surrounding fields and on the roof. Four iron ventilation ducts are the only visible signs of the former reservoir. The entire structure is covered in soil, with about eight inches on the roof.

Work is expected to start on the pounds 35,000 project in the next few months. The building will mirror the interests of its new owners, who run a sculpture, follies and mosaics business with an emphasis on Gothic design. It will have three bedrooms, a large cross-shaped central reception room, a kitchen, bathroom, library, cellar, and a stage for exhibitions and performances. The front door will be hidden in an underground hallway. A glass roof will provide light along with optic fibres under the floor.

North Devon council has agreed to the conversion, on condition that the pasture land remains untouched.

However, it was not the design that won over the parish and district council planning committees: they were most impressed by the building's environmental features. A water-wheel, fed by the old reservoir supply, will generate electricity. Eight brick columns inside the tank will absorb solar heat and release it throughout the day, providing central heating. This will also be used to heat water in plastic pipes. Most of the rubbish will be recycled and none of the structure is visible.

Mr Rodney-Jones said that most people laugh at him when he tells them he is going to live underground. 'Some think we are a bit strange, but it makes perfect sense to us. It will be an environmentally friendly building. I think it has turned out to be a very shrewd gamble.'

He and Ms Ridd are members of the British Earth Sheltering Association, formed in 1983 by three young architects in a 'remote hideout in North Wales' and committed to energy conservation and the development of environmentally friendly underground earth shelters.

Membership has grown with the general interest in conservation. According to Peter Carpenter, the association's secretary, there are now 250 would-be earth-shelterers.

'Some people feel they are going back to the womb or Mother Earth - I'm more interested in saving energy,' he said.

Some members have been subjected to terms of abuse such as 'hobbit' and 'mole'. As Mr Carpenter, who himself lives under 1,000 tons of earth in Monmouth, says: 'There's some negative feeling about the image of living underground because it's associated with caves, darkness, dampness and being trapped, but I see them as very bright, light, quiet and warm.'

The movement began in the United States as a response to the 1970s energy crisis. There are now 35,000 modern-day troglodytes in the US, while in Britain only seven earth shelters have been completed.

But, according to Mr Carpenter, interest is growing, and the 'moles' have recently found new role models. Lord Palumbo, the Arts Council chairman, is planning to spend his retirement in an underground palace currently being built on an island near Skye.

The award-wining architect Sir Norman Foster has also shown interest with his underground Crescent Wing completed at the University of East Anglia last year. The troglodyte's enemy is the council planner, who often refuses to consider radical underground developments. Since 1983, only 27 out of 50 planning applications have been accepted, according to Mr Carpenter. 'It is an uphill struggle,' he said.

(Photographs omitted)