MICROWAVES -- the unseen sound waves that are now the centre of so much controversy -- were sending information above the heads of Bolton people long before anyone had heard of mobile phones.

But the waves, which once helped to guard the nation from nuclear attack, never attracted any of the furore or health scares that now surround the widespread use of mobile phones and microwave cookers.

Walkers enjoying the solitude of Winter Hill have expressed new concerns to the BEN in the past week following the appearance of notices warning of danger, particularly to anyone with a heart pacemaker, in the close vicinity of masts.

But the National Radiological Protection Board has stressed that there is no new danger. The notices are in response to recommendations of the recent Stewart Committee on possible health risks of microwaves. The committee recommended clear warning notices at antenna sites.

Although the growth of mobile phones is a recent phenomenon for the general public, a microwave communications system was part of Winter Hill's "crown of thorns" for many years during the Cold War period. Among the conglomeration of television and communications masts that make the 1,498 feet hilltop a familiar landmark from almost anywhere in the old county of Lancashire, there used to be a link in what became known as The Backbone Chain. A microwave system, on the same lines as those that are now commonplace in the hi-tech world of mobile phone communications, was installed as part of a sophisticated but seldom-talked-about national defence system.

No one in high places ever admitted that was the case. Defence chiefs never discuss such things in public.

But there was never a challenge to the information in two best selling books about Britain's "secret" defence system which included maps showing Winter Hill as part of the "Backbone Chain" of communications sites.

Duncan Campbell's "War Plan UK" in 1982 and Peter Laurie's "Beneath the City Streets" a year later both showed Winter Hill to be part of the network of microwave transmitting sites which linked nerve centres, defence headquarters and bunkers all over Britain.

The main links were along the Pennines, but other spurs went off to the satellite hills of the backbone of England, such as Winter Hill and the North Yorkshire moors.

The system is thought to have been planned in the mid 1950s to counter the Cold War threat of H-bomb attack on Britain. The chain was complicated to account for possible destruction of some sites, Duncan Campbell claimed, so that communications could be maintained between military and civil defence installations.

Since the 1980s, the number of microwave transmitters on Winter Hill has grown considerably but local concern was raised recently when warning notices and diagrams of exclusion zones began to appear around installations that have been there for years.

Freelance photographer Phil Taylor, a keen hill walker, took photos of a new sign, near a BT antenna, warning people with "heart pace-makers or similar devices" to stay clear.

A diagram on the sign shows an exclusion zone hazard area to be heeded even by people who do not have a pacemaker.

But a spokesman for the National Radiological Protection Board said the Winter Hill signs were primarily for people working at the antenna sites and were similar to those now appearing at sites all over Britain. She said companies which operated transmitters were abiding by the recommendations of the Stewart Committee, published in May, which advise precautionary notices until long term studies of possible biological effects of microwaves are concluded.

But she said the effects of transmitters on heart pacemakers was already well known and, for that reason, antennae were not installed near hospitals.

Photographer Mr Taylor found that his electronic flash meter -- used to measure the light from a flashgun -- would not work properly within a hundred yards of the microwave transmitters.

A spokesman for the Army said Winter Hill was still used for normal radio transmission but "microwaves are not part of the system".

Even though is believed it is several years since the Backbone Chain system was scrapped, the Ministry of Defence in London would still not admit to the BEN that it ever existed.