On London's Downing Street, home of British prime ministers, the flags flew at half mast honoring the death of "a great leader," in the words of her Conservative successor, Prime Minister David Cameron.
While most political leaders across the spectrum offered praise, her erstwhile political opponents, including former London Mayor Ken Livingstone, criticized her leadership, which stretched from 1979 to 1990.
Thatcher, who won three elections, was defined by the battles she took on during the 1980s: she waged war against Argentina, clashed with striking miners amid high employment as parts of the north of the country that had been world centers of manufacturing declined.
Cameron called her a "titan" adding, "she didn't just lead our country, she saved our country." "The trouble is that almost everything that is wrong with Britain today is her legacy," Livingstone, who ran London's city authority when Thatcher was in power, told Sky News. "It was her that decided to deregulate the banks. She decided to let our manufacturing wither. She was fundamentally wrong."
Current Labour leader Ed Miliband took a conciliatory line, saying she was a "unique figure." "The Labour Party disagreed with much of what she did and she will always remain a controversial figure," he said in an e-mailed statement. "But we can disagree and also greatly respect her political achievements and her personal strength."
Britain's current generation of leaders entered politics in the 1980s either inspired by Thatcher or to oppose her. She inspired passion in some and loathing in others.
"She changed our country forever and all of us owe so much to her," Tory Foreign Secretary William Hague said in a post on Twitter. "A legacy few will ever equal. Rest in peace, Margaret." His colleague, Welfare Secretary Iain Duncan Smith, said Thatcher was "the reason I came into politics."
"She also defined the politics of the 1980s. David Cameron, Nick Clegg and I all grew up in a politics shaped by Lady Thatcher," Miliband said. "We took different paths but with her as the crucial figure of that era.
"Very few leaders get to change not only the political landscape of their country but of the world," former Labour Prime Minister Tony Blair said in an e-mailed statement. "Margaret was such a leader. Her global impact was vast. And some of the changes she made in Britain were, in certain respects at least, retained by the 1997 Labour government, and came to be implemented by governments around the world."
"Whatever side of the political debate you stand on, no one can deny that as prime minister she left a unique and lasting imprint on the country she served," Clegg wrote in an e-mailed statement. "She may have divided opinion during her time in politics but everyone will be united today in acknowledging the strength of her personality and the radicalism of her politics." Former Labour Party Home Secretary David Blunkett called Thatcher a "most formidable opponent." He was less flattering about her legacy. "I have to acknowledge her deep commitment to her own values and her determination, although, with Bernard Ingham at her side, she was the first modern exponent of carefully worked spin, which allowed her to present compromise as merely delay, and deep irritation with opponents in her own party as principled stance," he said.