Each Saturday night for the past two months, thousands of striking workers have gathered outside the brick and barbed-wire fortress housing the four British newspapers owned by international media baron Rupert Murdoch.

Shouting curses, the protesters carry placards accusing Murdoch of taking food from the mouths of their children. In a weekly shoving match with police, they surge into the surrounding East London streets, trying to block trucks carrying copies of the next day's Sunday Times to distribution points around the country.

Yet even leaders of the two print unions representing the workers know that the strike is largely futile. It was lost within hours after it began in January, when Murdoch announced that the more than 5,000 employes who decided to walk out -- half his work force -- were fired. That was an extraordinary act in modern British labor history in which trade unions have been virtually immune to the ultimate employer sanction.

In a series of actions without precedent here, Murdoch has brought to their knees what were widely considered the most aggressive and successful trade unions in Britain. Before they knew what hit them, the printers' organizations were subjected to heavy fines, had their assets seized in court and were barred from all but the most minimal action against his News International conglomerate.

For many here, Murdoch's assault was welcomed as the first all-out offensive of a third Industrial Revolution. If the first began more than 100 years ago with the rise of factories and smokestacks on the English horizon, the second came after World War II, when labor-backed governments worked to redress the grievances of the oppressed work force.

By the 1970s, labor had come to represent the status quo and when Britain began its steady decline as a manufacturing power, many held the blue collar bastions responsible. By 1979 -- the "winter of discontent," when striking public service workers left the streets piled with garbage and transportation ground to a standstill -- Britons were responsive to the get-tough platform of Conservative Party leader Margaret Thatcher.

While Murdoch is the hero of the third Industrial Revolution, Thatcher is its patron saint. In what she considers one of the greatest accomplishments of her 6 1/2 years as prime minister, Thatcher has provided management with the tools to break trade union power.

"Remember the circumstances under which we took over," Thatcher said in a recent television interview. "Industries overmanned, very restrictive practices, the trade unions had practically taken over Britain. You had strikes, you had the winter of discontent, you had a government unprepared to tackle the industrial problems.

"They didn't like to make the unpopular, difficult decisions. So we were in decline. Britain was defeatist. It was becoming ungovernable."

Thatcher moved quickly to turn the tide. Under a series of laws promulgated by her Conservative government between 1980 and 1984, the ability of unions to take "lawful and effective" action against an employer "has been reduced to zero," said Robert Simpson, a professor of labor law at the London School of Economics.

For the first time, unions were required to hold secret ballots of members to elect their leaders and to vote on any industrial actions rather than permitting wildcat strikes. Government funds were made available to pay for the balloting. Picketing was limited to only those workers on strike and only at their own place of work. All forms of secondary boycott were declared unlawful.

Some argue that the campaign against union power may have gone too far for what are, at heart, liberal British sensibilities. Although he acknowledged that "public opinion has a long way to go before it is very sympathetic to unions," James Prior, the Cabinet minister responsible for the first round of changes in 1980, warned that "it is very important that we shouldn't appear vindictive. Worms do turn."

Prior, who was ousted by Thatcher as employment minister in 1981 for being too soft on the unions, said in an interview that what the government should be looking for are "reasonable changes, that will last a lifetime" and not be immediately overturned once the Conservatives are out of power.

He and others noted that a dramatic drop in the number of industrial disputes in recent years could at least partially be attributed to massive unemployment here which, under Thatcher, has reached the highest rate in British history.

"You are much more likely" not to strike, Prior noted, "if you think that when you lose one job, you might not get another."

But the government maintains that newly released statistics prove the stabilizing success of its laws. During the peak year of 1977, an average of 225 disputes began each month. Last year the monthly average was only 69. Even with the year-long coal miners' strike continuing into the first three months of 1985, the total number of working days lost to job action last year was only 6.4 million, compared to 29.5 million in 1979.

The protracted miners' strike was a landmark in the decline of union power here and a major boost to Thatcher's union policy. The strikers' confrontational tactics led to violence and a massive loss of public support. A court sequestered the union's assets, and heavy financial penalties under the new legislation dealt heavy blows to a union that historically had occupied a special niche in Britain's labor movement.

The very idea of putting trade unions inside a legal framework was antithetical to British history, primarily because that is the way the unions wanted it.

"What the law hasn't given, the law can't take away," was the union philosophy, said labor law professor Simpson. Even the right to strike is excluded from British law, as trade unions have relied on their own indispensability to bring employers to heel.

The strike by the National Union of Mineworkers, which ended in March last year, was the first significant test of Thatcher's new policy. Striking coal miners were arrested under laws against secondary action when their union organized so-called flying pickets, traveling from mine to mine to pressure nonstriking workers to join them. Severe financial penalties and contempt of court citations also were imposed. Significantly, the union's pleas for public backing fell on largely deaf ears.

The miners were perceived ultimately to have lost the strike, called to protest the closure of unproductive mines. But they are technically public workers, employed by the state-owned National Coal Board in a vital and labor-intensive industry and knew the government could not afford, either politically or economically, to let them go permanently.

The vast majority of private sector employers, like the government, have never taken advantage of their right to fire striking workers.

"They wanted to have a labor force at the end of the dispute," Simpson said. "Murdoch didn't, at least not this labor force."

It was not until Murdoch that the ability to fire workers, plus Thatcher's new trade union legislation, were used as a package. Implementing a strategy that was three years in the planning, Simpson said, "Murdoch simply took the law to its logical conclusion," as employers throughout the nation looked on in amazement and admiration.

The attention was particularly acute in Fleet Street, where the powerful print unions had never lost a job action. As far as the nation's publishers were concerned, the Murdoch treatment couldn't have happened to more deserving workers.

Even Brenda Dean, head of the larger of the two print unions, the Society of Graphical and Allied Trades, acknowledged that support for their strike by both the public and other unions is minimal.

"There is a feeling that they've gotten their comeuppance," she said of the workers she leads. "I can understand that."

Stories of print union power and perfidy are legion in Fleet Street -- of payrolls padded with names like "Mickey Mouse" and "Donald Duck," of refusal to print because workers did not like what a newspaper said.

Harold Evans, former Sunday Times editor and now editorial director of U.S. News & World Report in Washington, recalled in a telephone interview a well-known 1977 incident when more than a third of the 1.5 million press run -- containing the paper's big scoop on Thalidomide and birth defects -- was lost. The National Graphical Association, the second print union, shut down the presses at midnight Saturday to demand more money.

"The British print unions have got what they deserved from Rupert Murdoch," Evans said. "Thank God it's come; I wish it had come in my time. I don't have the slightest sympathy for any of them."

Current Sunday Times editor Andrew Neil is equally unmoved by union grievances. The print unions, he said, "represent everything you could imagine that is worst about Britain. It has always been my ambition to bust [them] and we did it. It would have been nice to take the reform way. But people who thought that was possible don't live in the real world."

The unions' crisis with Murdoch came when he proposed to move operations for two of his papers, The Sun and News of the World, from Fleet Street to a newly equipped building at Wapping, in the old East London dock area along the Thames River.

The two print unions insisted on negotiating the move, fearing that it was a ruse for installing new technology at the cost of jobs. Such computerized operations are used widely in the United States and elsewhere but until recently were not found in Britain.

Murdoch maintains that he tried for six years to negotiate the move. Print union head Brenda Dean said Murdoch consistently avoided substantive negotiations and manipulated the strike so he could instantly shed thousands of workers and maximize his profits. Dean said her members -- including thousands of clerical and warehouse workers, in addition to printers -- were ready to bite the bullet on new technology.

But Murdoch, she said, "just wasn't interested . . . The worst thing that could have happened" for Murdoch's plans "would have been successful negotiations with us."

In January, Murdoch announced that the Wapping facility was ready to open and that henceforth The Sun and News of the World would be printed there. The unions protested. They held -- and won -- a strike vote.

In response, Murdoch moved all his operations to Wapping. There, inside an old dock warehouse long closed to public view by barbed wire and security guards, he had secretly installed new computerized systems and presses large enough to accommodate production of all four newspapers.

Employing a greatly reduced new staff of secretly trained members of the electrical engineers union -- less militant than the printers and less fastidious in their concern for labor solidarity during the current period of high unemployment -- he fired all striking print union members.

When the workers tried to picket other Murdoch offices outside of Wapping -- including Murdoch-owned suppliers and distribution networks -- it was declared illegal.

Long in advance, Murdoch had diversified his operations under a series of newly registered, separate companies. Any picket against them -- or attempt to inhibit their operations -- was a violation of the law against secondary actions. Nor can other unions honor the printers' action with solidarity strikes. All such actions now are illegal.

Other papers with modernization plans long in mothballs have turned tough. The Daily Telegraph and Sunday Telegraph last month announced that they would move all printing and editorial operations to a new building in central London, with "substantial" job cuts to save costs. The Daily Mirror is moving to a new plant in the dock area and already has cut half of its 6,000-person work force.

Murdoch's move also has posed serious questions for the opposition Labor Party and the powerful Trades Union Congress that supports it. While pledging to repeal much of the Thatcher revolution once they get back into power, they have begun studying the possibility of legislating "positive rights" for workers. The change is significant because the establishment of a legal "right to strike" implies that there are times when workers cannot claim such a right.

In a minor success for the print unions, Murdoch has agreed to negotiate over a token number of jobs at his other operations.

But even union leader Dean acknowledged that they have lost the larger battle. "It's going to be a very, very difficult thing" for members to face up to the fact that most of them are out for good, she said.