The Ministry of Defence believes it has found the perfect weapon in the battle against terrorism in Northern Ireland: airships. The department has bought a blimp, the first of a planned fleet of four, which will be fitted with a battery of sophisticated surveillance systems to penetrate the secretive activities of the province’s paramilitary gangs.

Cruising silently through the skies for up to 24 hours at a time, the six-strong crews will be able to eavesdrop on conversations below, observe the movements of terrorists and film suspicious activities. They will fly at up to 5,000 ft., out of range of small arms fire.

A contract has just been signed for the first airship and, if trials prove successful, a further three will be ordered, said a ministry source. Technicians will put the blimp through its paces at the government research establishment in Boscombe Down and in Northern Ireland later this year. They want to test the airship in winter to see how it responds in difficult weather conditions.

The 194 ft vessel, a Skyship 600 christened the Prince of Wales, has few similarities with the famous airships flying before the Second World War. The most famous of those, the Hindenburg, crashed in flames in 1937 with the loss of 36 lives, ensuring the eclipse of the vehicle for military or civilian transport.

To eliminate the fire risk, the Skyship is filled with non-combustible helium. There is little pressure difference between the helium and the outside air, so it would gradually deflate if struck by bullets.

The idea of using airships over the province has been considered for years but has previously collapsed under what one official called "the giggle factor". He added: "It was just difficult to get people to take it seriously. But the fact remains that it is the perfect platform for all kinds of operations."

Once it enters service, the airship should improve the surveillance capability of the security forces. Until now, they have relied either on ground surveillance, using informers, undercover troops and various technical systems, or on aeroplanes and helicopters. Such aircraft, however, are noisy, need regular refueling and are too cramped to house adequate sensory equipment. The IRA has also become adept at finding methods to counter ground surveillance.

Defence strategists believe the airship may give the security forces the initiative against the paramilitary groups by forcing them on to the defensive.

The airship’s arsenal will include thermal imaging systems to identify and track people at night, directional microphones to intercept conversations, image intensifiers and powerful cameras. It will also have scrambled communications equipment to allow the crew to call in security forces to deal with any crisis on the ground, and to co-ordinate activity from the air.

The Prince of Wales has been bought from a consortium led by Westinghouse Surveillance Systems. "The MoD order is a vindication for the airship," said George Spyrou, chairman of Airship Management Services, which supplied the airframe.