LONDON, JULY 18 -- Prime Minister Margaret Thatcher has lost more than a trusted political soulmate with the sudden departure of cabinet minister Nicholas Ridley. She has lost some political power as well, within her own government and her party.

Analysts and commentators here say Ridley's resignation over the weekend, after an outburst of anti-German remarks in a Spectator magazine interview, leaves her without a senior cabinet colleague who shares her deep suspicions and visceral hostility toward a united Germany and a federalized Europe.

The Ridley affair also underscores, many argue, the extent to which Britain under Thatcher has been marginalized by the end of the Cold War era and the increased pace of European economic and political union.

Ridley's resignation, says columnist Hugo Young, is Thatcher's "most significant" political loss since she took office 11 years ago. "It marks the end of an era," wrote Young in the Guardian Tuesday. "Life for Mrs. Thatcher, and therefore for Thatcherism, will never be the same again."

When Ridley resigned, Thatcher's acceptance letter expressed regret over "the great gap which your departure will leave." Insiders say that was not just the standard rhetoric. Ridley, a 60-year-old political infighter, was not only her closest cabinet ally but a weapon she used to battle colleagues whose views she did not always trust.

He sat on several key cabinet committees, they say, including the group of four -- the others being Chancellor of the Exchequer John Major, Foreign Secretary Douglas Hurd and Thatcher -- that last month drew up Britain's alternative to a joint European currency.

With Ridley gone, Major, Hurd and their allies, including Christopher Patten and Sir Geoffrey Howe, are expected to keep the pressure on Thatcher to accede to closer cooperation with Britain's European partners that would bring with it an inevitable loss of British sovereignty. One likely result, say many analysts, is that Britain will join the exchange-rate mechanism of the European Monetary Union sometime in the fall -- despite Thatcher's previous resistance to the move.

Britain's role in Europe has long been a subject of contention inside Thatcher's government and her Conservative Party. Fiercely proud of her own achievements in reintroducing free-market principles to Britain, Thatcher is said to fear her country would lose both power and freedom of choice if it became an appendage of a monolithic Europe, inevitably dominated by Germany.

Others in the party fear just the opposite: that Britain will be left stalled on a side track if it does not get on the European supertrain. They see the collapse of the Soviet Bloc and the new economic muscle of a united Germany as signs that Britain must accept a reduced status as a middle-ranking power or lose all influence in shaping the new Europe.

"Prickly independence has come to appear more and more like futile isolationism," wrote the respected Financial Times. British cabinet ministers, it said, "are coming face to face with the consequences of being in charge of a not very large, not very successful country."

These are not just theoretical questions here. Most of the major political crises of recent years -- from Michael Heseltine's resignation as defense secretary in 1986 to Nigel Lawson's as chancellor of the exchequer last fall -- were precipitated by clashes between Thatcher and senior Conservatives over European issues.

In her vocal unease over European integration, many analysts contend Thatcher has stood in the minority within her own party. Many believe that there are no more than 40 or 50 hard-line "anti-Europeans" within her party's House of Commons bloc of about 370 members. Few party members came to Ridley's defense over the weekend when friends tried to rally enough support to keep him in office.

Similarly, despite an outbreak of patriotic feeling during the 50th anniversary of the Battle of Britain, anti-European and anti-German sentiment does not seem to be playing well in the polls. A Gallup opinion survey in the Sunday Telegraph showed that 68 percent of respondents rejected Ridley's claim in the Spectator that proposals for European monetary union were "a German racket to take over Europe." About 66 percent said they trusted the German people -- compared to only 50 percent who expressed similar trust of the French.

Thatcher's supporters dismiss talk that her own standing has been damaged by the Ridley affair. "She supposedly has been weakened so many times in the past 10 years, but she always seems to come out stronger," said a senior aide. "It's a sad day that he's gone but I don't think she's weakened politically."

Others contend Thatcher was able to get away with anti-European rhetoric and tough stances during the mid-1980s, when the British economy was outstripping most of Europe's and Thatcher's standing with the United States and public opinion polls at home was unassailable. But by this account, now that the economy has suffered a relapse -- Major has warned that a 10 percent annual inflation rate is just around the corner -- and George Bush has cooled the American love affair with Britain, Thatcher must be more cautious.

"She knows she's in a minority on this issue," says former foreign secretary David Owen. "She has to watch her back, and her back is Europe."

Owen says Thatcher already has recognized her vulnerability and acceded to the Europhiles, led by Major, Hurd and party chairman Kenneth Baker. All of them are skillful political operators who have been careful not to show up the prime minister in public while gently maneuvering her toward accepting accelerated European integration.

But to some, Ridley's departure underscores her isolation and ultimately suggests that Thatcher, for a decade the epitome of the fiercely independent leader, has lost personal control over her government.

"Increasingly her writ will not run: being obstructed and countermanded by Brussels, whose invasions she cannot stop, and by colleagues who have her in a kind of prison," wrote the Guardian's Young. "Now her spur and conscience, the most serious friend at her court, the guarantor that gray compromise need not prevail, has departed."