When Ronald Reagan is formally eulogized at Washington National Cathedral Friday and his body then flown home to southern California for burial, one of the honored mourners will be his ideological soul mate and closest international friend, former British prime minister Margaret Thatcher.

Baroness Thatcher of Kesteven, as she is formally known here, is 78 years old and in frail health, having suffered a series of small strokes in recent years. Her doctors have sharply curtailed her travel and banned her from public speaking. But friends say she was determined to come to the United States to bid farewell to the man she called in a statement Saturday "one of my closest political and dearest personal friends."

Dressed in black, she paid a visit Wednesday to the Capitol Rotunda where Reagan's body lies in state, touching the coffin with her right hand and curtsying solemnly.

Earlier this year, she videotaped a seven-minute tribute to Reagan whose soundtrack will be played as an official eulogy to people attending Friday's service. Then she plans to fly to California with the Reagan family for the 40th president's burial at sunset at the Reagan Library in Simi Valley.

"I don't think they could have kept her away," said Bernard Ingham, Thatcher's press secretary during her 11 years in office. "This was a very special friendship."

The two leaders were conservative icons and Cold War partners -- Thatcherism was at least as strong a movement here as Reaganism was in the United States -- and their reputations and legacy have been much debated since they left office. But while Reagan's tenure came to its natural conclusion at the end of his second term in 1989 in an atmosphere of good feeling and gratitude, Thatcher was forced to resign the following year after a sizable part of her ruling Conservative Party turned against her.

Under her successor, John Major, the party went on to govern Britain for seven more years. But the wounds caused by Thatcher's political demise never really healed. Major and the Conservatives were roundly defeated by the opposition Labor Party and Tony Blair in 1997, and the party has since changed leaders three times, searching for one who could come to grips with Thatcher's legacy and recapture her winning electoral strategy.

"She was a divisive figure, and they've never really recovered from her loss," said Robert Worcester, chairman of the MORI polling group here. "She was the pilot, the navigator, the bombardier, and on occasion she was the tail-gunner as well."

Thatcher often added to her party's disarray by taking calculated swipes at Major and other party leaders who she felt had strayed from conservative principles. In some ways, she once acknowledged, she had more impact on Blair, who remade the formerly socialist Labor Party into a more centrist institution, than on her Conservative successors.

Strokes have robbed the former prime minister of some of her short-term memory, friends say, and curtailed her once-hectic travel schedule. Under doctors' orders she has also stopped the relentless round of speeches that was netting her at least $50,000 a night. Her husband, Denis, died last June, and at his memorial service in October she appeared frail and tearful, clutching the arm of her son, Mark, for support.

"Denis was the ideal consort, her admirer and protector, and his loss was a great one to her," Worcester said.

But Thatcher was not too frail to defy doctors' orders last month and speak at a banquet honoring the 25th anniversary of her accession to power in 1979. She used the occasion to praise the "brave and inspiring leadership" of the new Conservative leader, Michael Howard, rip into the Labor government as tax-and-spend addicts and divulge what she called "a well-kept secret."

Journalist William Deedes, 90, a close friend of both Denis and Margaret Thatcher, said she always displayed a much more rigorous and prickly intellect than the affable Reagan. But he said the two leaders shared one key personality trait: "They were both good in adversity, and that's a factor that drew them close together," he said. "Anyone in politics can cycle downwind. It's cycling upwind that tests them -- and both had the ability to cycle upwind with a smile."