British journalists are already calling the $140 million printing plant "Fortress Murdoch." Surrounded by a 10-foot wall, a moat and coils of barbed wire, it is at least as well protected as the medieval Tower of London just down the road.

The extraordinary security precautions in force at the new London headquarters of Rupert Murdoch's worldwide newspaper empire are one indication of the high stakes involved in the most dramatic confrontation between unions and management in Britain since last year's unsuccessful strike by 185,000 miners.

It is widely accepted here that the future of the British newspaper industry depends on the trial of strength now under way between the Australian press tycoon and the trade union movement.

After months of secret preparation for the introduction of computer-based technology, last weekend Murdoch dismissed 5,000 print workers who went on strike after refusing to agree to a new labor contract. He then switched publication of his four British titles, including the prestigious Times of London, to his new printing works in the East London suburb of Wapping, over a mile from the old Fleet Street offices and their traditional hot-metal printing processes.

As the dismissed printers frantically lobbied other trade unions for support, Murdoch claimed almost total success in his attempt to accomplish what amounts to a long-delayed technological revolution in the British newspaper industry. Speaking on television, he said that the Wapping plant had succeeded in publishing a full edition of The Times and "99 percent" of the normal run of The Sun, a racy, mass-market tabloid.

Acknowledging that some readers were still not receiving the papers because of distribution problems, he added: "I think out in the field there are still a few rough edges, but in another few days, we will have it going very smoothly."

Murdoch's confidence of ultimate victory over the print unions is in part a reflection of the almost military thoroughness with which the entire operation was planned, according to industry analysts here. To ensure complete surprise, a U.S. company, Atex, was hired to install the $10 million worth of computer equipment. The workers operating the machinery are bused from outside London and supervised by Americans and Australians.

The relative ineffectiveness of union protests over the past week is also interpreted here, however, as a sign of a crucial shift in the balance of power between management and organized labor over the past year. The shift has occurred partly as a result of the high level of unemployment, which now stands at over 13 percent, and partly because of tough antistrike legislation introduced by Prime Minister Margaret Thatcher's Conservative government.

The scene outside the Wapping plant seemed to bear out Murdoch's calculations. At the main entrance, there were only six official pickets, watched by an equal number of police and security guards. Some 200 yards away, several dozen supporters tried to keep their spirits up by shouting anti-Murdoch slogans at traffic heading in the direction of the complex.

"This is an obscenity to the British way of life," complained a member of the SOGAT printers' union, Jack Payne. He gestured at cameras, positioned inside the complex, that followed the movements of the strikers. "This is a very traditional industry. We accept change, but it should be a humane change. Murdoch is trying to throw people who have worked for him for years onto the scrap heap."

A truck carrying paper for the plant headed through the front gate despite firm instructions from the drivers' union not to cross the picket line. Following close behind was a luxury coach with drawn curtains hiding newly hired workers, most of whom belong to an electricians' union that has refused to join the SOGAT-led strike against News International, the Murdoch parent company.

"Look at them, they should join the national union of Judases," said Payne.

Bruce Matthews, managing director of News International, attributed the lack of union solidarity to a widespread feeling that the printers are a privileged and pampered group of workers who have been able to impose their will on Fleet Street managements for too long.

"There was much more sympathy for the miners than the print workers. If you took a poll, I suspect you would find that the print workers would rank fairly low in terms of popularity with the public," he said.

According to Matthews, one of several Australians appointed to top management positions by Murdoch, overstaffing in Fleet Street is sometimes excessive. He cited the example of a folding machine that was staffed by 22 persons at the old plant but by four in Wapping.

In an editorial earlier this month, the London Sunday Times, also owned by Murdoch, said Fleet Street offered "a microcosm of Britain's industrial malaise at its worst: ridiculous overmanning, absurd restrictive practices, pusillanimous management, top-of-the-league pay levels which bear little relation to the work done or the skills involved, and the technology of the 19th century."

While many journalists would agree with this description of the British newspaper industry, there has also been some resentment at what are perceived as Murdoch's high-handed methods. Last week News International failed to consult journalists on the move to Wapping, offering them a straight choice between dismissal if they refused and a $2,000 bonus and free medical insurance if they complied.

Despite the threat of dismissal, about 30 journalists turned down Murdoch's offer and are camping out at the almost deserted Fleet Street offices while colleagues attempt to mediate.

Murdoch's coup -- presenting the unions with a fait accompli -- has been followed with a mixture of excitement and concern by other newspaper proprietors, who now face much stiffer competition from News International. The move to Wapping allows the four Murdoch papers, which already account for a quarter of Britain's total national newspaper circulation, to expand their advertising revenue by increasing the number of pages.

Several other newspaper groups, including the Daily Telegraph and the Daily Express, are studying the possibility of moving out of Fleet Street. An entirely new national newspaper, Today, is due to make its appearance in March, using computer technology and presses outside London