From the outside, Benham Valence is certainly impressive: a gleaming, honey coloured, porticoed mansion designed by Henry Holland and set in manicured gardens by Capability Brown. Across the gravel drive, a lawn gently slopes down to a section of the river Kennet famous for its brown trout.

But what makes Benham truly remarkable lies inside. A year ago the house, famous in 18th century high society, was almost derelict; now it has been rescued and transformed into the most technologically advanced stately pile in the country.

Using cutting-edge wireless computer networks, a technology still in its infancy, Benham's new tenant, the computer company Prime Business Solutions, has spent over £1m turning it into a state of the art headquarters complex, and heritage organisations are hoping the Benham model will offer a lifeline to other endangered historic buildings too.

Casual visitors to the house, just outside Newbury, would find no difference between the huge ground floor public rooms now and how they looked almost 230 years ago.

The gilded coving and cornicing on the walls and ceilings have been reconstructed. The original marble fireplaces are still there and the tall windows look on to an immaculate sunken garden, complete with Italian stairway and sculpted hedges.

The clever stuff, however, is invisible. Most of the house's 18,000 square feet are "live". From almost any spot, it is possible to get instant access to the computer systems, the internet or email via a network of small radio base stations tucked away in cupboards.

The system is so powerful that users can stand in the middle of the enormous ballroom with a laptop and get high speed live video streamed on to their screen without using a single cable.

Even the telephone system is wireless. Instead of using conventional handsets wired through the walls, Benham boasts internet protocol phones, which operate through software on the computer network.

The result is that any member of Prime's staff can work anywhere in the building and still have access to their telephone, email and everything they would have had at their desk. They can also take and make calls from their work telephone anywhere in the country with access to the internet.

The system is the latest example of convergence technology, voice and data traffic in a single network, which is likely to be at the centre of the next phase of the communications revolution.

The trigger for Benham's hi-tech rebirth was its Grade 1 listed status, which severely restricted what alterations residents could make and was one of the reasons the house lay empty for so long. The stone floors could not be dug up nor the ceilings be lowered to install the miles of cabling needed to bring such a large building into the 21st century.

Built in the 1770s for Lord Craven, Benham was once one of the most fashionable houses in southern England. The future George IV was a visitor, and Samuel Johnson.

But the last family to own it, the Suttons, moved out just before the second world war and for 60 years it lay empty for long spells. By the time Prime's directors first saw the house last summer, it was in a sorry state. The gardens were overgrown and the stonework was crumbling. The interior was worse.

Prime realised, however, that it could design the technology it needed without undermining the integrity of the building. When a 15 year lease was agreed, the owner, a big pension fund, was able to plough in the investment to restore the place.

The network, which has just won a prestigious industry award, is designed to keep communications completely secure, overcoming one of the flaws of wireless.

The base stations and antennae are positioned so that radio signals do not leave the building, preventing anyone outside tapping into voice or data traffic. Communications are also encrypted, and the code is automatically changed every few hours.

These advances have raised the hopes of preservation experts that other historic buildings left to rot can be saved too.

Jason Turner, of the National Trust, said: "If people can use new technology to breathe new life into an historic property without damaging its integrity, then that has to be a good thing."

State of the art

• Wireless computer network: terminals and internet connected via discreet radio base stations, no intrusive cabling.

• Convergence technology: voice and data carried on the same network, removes need for separate exchanges.

• Internet protocol telephones: run through software on computers, not handsets. Users dial using virtual keypad on screen, and talk and listen through headset. Allows users access to their own phone anywhere.

• Security: radio base stations and antennae prevent radio signals escaping beyond the house. All voice and data traffic encrypted.