A sampling of cases illustrates the impact of these measures:

• In 1973 a young man running on a road at night was stopped by the police and found to be carrying a length of steel, a cycle chain, and a metal clock weight. He explained that a gang of youths had been after him. At his hearing it was found he had been threatened and had previously notified the police. The justices agreed he had a valid reason to carry the weapons. Indeed, 16 days later he was attacked and beaten so badly he was hospitalized. But the prosecutor appealed the ruling, and the appellate judges insisted that carrying a weapon must be related to an imminent and immediate threat. They sent the case back to the lower court with directions to convict.

• In 1987 two men assaulted Eric Butler, a 56-year-old British Petroleum executive, in a London subway car, trying to strangle him and smashing his head against the door. No one came to his aid. He later testified, "My air supply was being cut off, my eyes became blurred, and I feared for my life." In desperation he unsheathed an ornamental sword blade in his walking stick and slashed at one of his attackers, stabbing the man in the stomach. The assailants were charged with wounding. Butler was tried and convicted of carrying an offensive weapon.

• In 1994 an English homeowner, armed with a toy gun, managed to detain two burglars who had broken into his house while he called the police. When the officers arrived, they arrested the homeowner for using an imitation gun to threaten or intimidate. In a similar incident the following year, when an elderly woman fired a toy cap pistol to drive off a group of youths who were threatening her, she was arrested for putting someone in fear. Now the police are pressing Parliament to make imitation guns illegal.

• In 1999 Tony Martin, a 55-year-old Norfolk farmer living alone in a shabby farmhouse, awakened to the sound of breaking glass as two burglars, both with long criminal records, burst into his home. He had been robbed six times before, and his village, like 70 percent of rural English communities, had no police presence. He sneaked downstairs with a shotgun and shot at the intruders. Martin received life in prison for killing one burglar, 10 years for wounding the second, and a year for having an unregistered shotgun. The wounded burglar, having served 18 months of a three-year sentence, is now free and has been granted £5,000 of legal assistance to sue Martin.