Most elderly couples looking to downsize to a single-storey home in readiness for their twilight years would choose a bungalow that needs no work doing to it.

David and Diane Rasche, 77, are defying convention to have an home built for them that’s so ultra-modern it will look like giant rocks embedded in moorland.

The unorthodox country house near Ilkley in West Yorkshire is designed to look like a cave rising from the landscape, but with vast floor-to-ceiling windows giving views over the moor, as well as outdoor and indoor pools.

The four-bedroom property, which will be created using gritstone from local quarries, will be named Fomorian. In Irish mythology, the Fomorians were a race of supernatural, monstrous beings and giants, but the idea was inspired by mythical giant Rombald who is said to have lived on Ilkley Moor.

Architect Matt Masserella-Gill said: “We took cues from local folklore, the surrounding rocks; ancient carvings, standing stones and escarpments that are synonymous with the landscape.”

The couple commissioned the house for four acres of land in the grounds of their 14.5-acre estate, on the edge of Ilkley Moor, after struggling to find the mod­ern home they wanted in the area.

The green-belt land is in the South Pennine Moors Site of Special Scientific Interest, the South Pennine Moors Special Protection Area and Special Area of Conservation, and has been designated as a new National Nature Reserve.

As a result, Ilkley town council recommended the plans be refused, warning the building would be a “visual anomaly” in the landscape.

Bradford council rejected the plans twice before a government planning inspector allowed them on appeal, under a rarely used planning law that allows a country mansion on green belt land if it “significantly enhances its immediate setting”. The inspector called the design, which looks like a series of boulders, “truly out­stand­ing”.

Architect Matt Massarella-Gill said that when they were commissioned, he and his team “let their imaginations run riot”.

“We asked ourselves, ‘What is our gut feeling?’ I sort of went completely mad and got the plasticine out and started sculpting because, in this day and age of computers and everything, it all felt too restrictive,” he told .

Architects Shaw & Jagger say they wanted the house to look like “part of the moors, its geology and its spirit”. It’s designed to have ultra-low energy usage, like homes built to “Passivhaus” standards.

Mrs Rasche told that her seven grandchildren, who are aged between 11 and 18, described it as “a bit of a Bond villain layout” or a bat-cave.

“If you’d asked me three years ago, ‘Do you want something absolutely radical?’, I’m not sure I would have said yes. But this is something architecturally outstanding,” said Mr Rasche, a tech entrepreneur.

Once the home is built, in about two years’ time, the Rasches will sell their existing mansion.