Whole buildings could be made invisible to radar - if the creation of a Hampshire inventor is as good as he says.
David Barker has spent more than 100,000 over the past decade on a peculiar 'hobby' - trying to come up with a way to make concrete soak up radar and other electro-magnetic waves.
Now, with the help of the Building Research Establishment, the accountant from London Road, Horndean, thinks he's cracked it.
He said radar-absorbent building blocks have obvious uses for the military: 'If you had a command and control centre out in the desert, you'd be able to lose it,' he said.
But he claims this could not just be the beginning of 'stealth buildings'.
His invention, created under the name of his firm Electro Conductive Concrete, could also have crimestopping uses as well.
Mr Barker, 63, said: 'It absorbs electromagnetic radiation, that's where it's a real killer. Everything else reflects it.
'That's radar, the signals which your computers give off, or any piece of electronic equipment. It stops mobile telephones from working, so you could use this to build prisons.
'If you're a villain it's possible to get a witness sorted out from prison using a mobile, or to carry on drug dealing.'
Signal-blocking windows and doors already exist, but he said this new concrete allows the walls to become signal-proof too.
All this sounds like fantasy, but computer engineering expert Dr David Ndzi, from the University of Portsmouth, told The News that, in theory, it is possible.
Plus Mr Barker has been backed in his research by the Building Research Establishment, the 90-year-old not-for-profit company which promotes better building practice.
The body has allowed him to use its Woking facility to test the strange concrete.
Guy Hammersley, chief executive of division BRE Ventures, said: 'Traditionally you have to build a room, and then come along and line it very expensively.
'This is very significant.
'It makes it possible to build whole buildings which are screened, which at the moment is almost prohibitive in cost.
'There's a growing demand for this.
'There are companies that are concerned about other companies spying on them, hospitals which want to prevent scanners from penetrating other parts of the building, or the potential use for building a prison.'