London — After 12 weeks of industrial confrontation, Britain's coal miners' strike is rapidly becoming a major law-and-order issue for Prime Minister Margaret Thatcher.
The problem facing her government was typified by the arrest of the miners' national leader, Arthur Scargill. Police took him from a protest march and charged him with obstruction.
Simultaneously, striking miners forced their way into the National Coal Board's London headquarters and occupied the building for several hours. They were later cleared by police.
Twenty-four hours earlier police in south Yorkshire clashed with 7,000 militant miners personally led by Mr. Scargill, who later complained about ''scenes of almost unbelievable police brutality.''
The miners' protests were finally put down by police on horses, and Prime Minister Thatcher spoke of the threat of ''mob rule.''
The government's problem is that in the Yorkshire coal fields where the strike is biting hardest, coal must be brought into steel plants to keep them burning. Miners have been picketing the plant in attempts to prevent coal trucks from getting through.
Under industrial laws introduced by Mrs. Thatcher, the National Coal Board could seek court injunctions against the pickets, many of whom come from far-flung areas. But the board, led by Anglo-American industrialist Ian Macgregor, has so far not tried to enforce action against picketing miners.
This has meant police must turn up in large numbers at trouble spots where they enforce traditional laws. More than 1,000 police equipped with riot gear were deployed at the plant near Sheffield where Mr. Scargill was arrested.
Ironically, the flare-up between police and miners came as secret talks were being planned between the coal board and Scargill's union. Apparently Scargill was trying to boost the morale of his followers by appearing on the picket line.
Two weeks earlier his wife had joined other women in staging a protest. She was arrested by police and ordered by magistrates to stay away from industrial clashes.
Mrs. Thatcher appears confident that the coal board will eventually get the upper hand over the miners. In the meantime police are being stretched to the limit.
The incidents near Sheffield caused injuries to 64 people and led the chairman of the police federation, which represents the interests of police officers, to call on the coal board to ask the courts to enforce restraining orders under the Thatcher industrial laws.
Demands on police have been so heavy that the government has already had to pay several million pounds to police authorities in the coal fields to help them foot the bills for extra police work.