Take, for example, the measures protecting a senior judge - a composite figure rather than a specific individual. He lives, say, in a prosperous part of Co Down, which is seen as the safest part of Northern Ireland since it is a considerable distance from any strong republican area. His substantial detached house is surrounded by a high fence, on top of which are closed-circuit television cameras. The security gates are electrically operated and illuminated by high-powered lights.
Around the fence and in the garden are sophisticated electronic sensors designed to detect movement. A wooden hut in the grounds houses RUC guards armed with automatic rifles.
The well-lit door of the house is heavy and reinforced. The windows are so thick that when tapped they emit not a pinging sound but a dull thud. There are more cameras high on the walls of the house, and there are other mysterious electronic devices whose functions are not clear.
Inside there is also a panic button which can be pressed to summon instant help in emergencies. Last year the wife of a prominent politician saved her husband's life by pushing the button when a republican assassination squad burst in and settled down to wait for the husband's arrival home.
Domestic staff are vetted by police, and many aspects of life are subject to security scrutiny. The guards consider whether events such as funerals or the wedding of the judge's daughter may create a risk.
Hospitalisations require special arrangements. Plans for overseas travel are not made through regular travel agencies: five years ago the IRA assassinated a senior judge and his wife as they returned from a holiday abroad.
The judge travels to court in an armour-plated car with a police driver who avoids certain districts and varies times and routes. In many of the courts, a large transparent screen separates the judge from the public gallery.
In the 'supergrass' cases of the early Eighties the judge was flanked by policemen with rifles as he conducted the cases. Some judges are said to have worn bullet-proof vests beneath their legal robes.
It is not known whether any judges carry guns, although several thousand personal protection weapons have been issued to various classes of people at risk.
This is a picture of what might be called the full treatment: the complete range of measures that the Government can take. Some individuals, however, simply refuse all or most of these precautions, preferring to attempt to keep a larger element of normality in their lives.
Others are always nervous. One former Northern Ireland Office minister is remembered by security sources as being 'utterly paranoid' and never satisfied with his security arrangements. Several sources confirm the story that he wanted to demolish a large house close to Belfast airport because he feared the IRA might take it over and launch an attack on him.
It is not only VIPs who are at risk. The IRA attacks off-duty police officers, off-duty soldiers, those who carry out work for the security forces, and on occasion people such as civil servants and prison officers.
The other side of the coin is that while so many people fear attack from republicans, republicans themselves are also clearly in danger. Particularly in recent years, a steady stream of Sinn Fein representatives and supporters have been killed or injured in attacks by loyalist groups.
The Sinn Fein president, Gerry Adams, for example, was hit by three bullets while driving through Belfast city centre, and a court was told recently of another plot to kill him by fastening a limpet mine to the roof of his taxi. In the back streets of Belfast, republicans - and loyalists - now try to protect themselves just as the judge does in Co Down.
A composite picture of a Sinn Fein household in west or north Belfast starts with a front door that has been strengthened by a sheet of toughened glass screwed into its back. An iron drop-bar is put into place at night.
Beyond this is another door, made of steel and designed to withstand the sledgehammers that loyalist assassination squads sometimes use to break into a house.
Around the stairs is some fancy wrought-ironwork, but its purpose is not decorative. At night, when the family goes to bed, it is swung across the bottom of the door and locked so that gunmen cannot get up the stairs.
At a conservative estimate, at least 20,000 people in these categories are in danger. Most of these take some security precautions, in particular strengthening their doors, varying their routines, and checking underneath their vehicles for under-car booby- traps.
Some complain, however, that the authorities are not willing to give them proper help. One well- known politician said privately last week that he had asked the Northern Ireland Office and the police for protection but had been told they did not think he was in danger.
He contrasted this with what happened when he visited the Irish Republic: 'When I go down south the Guards are all over me like a rash, but when I cross the border into the North I'm on my own again.'Reuse content