Former US Secretary of State Henry Kissinger telephoned Thatcher in a very "emotional state" and the Soviet Union President Mikhail Gorbachev expressed "consternation", the file released by the National Archives said.
The file titled 'The Resignation of the Prime Minister, Margaret Thatcher', lays out the behind the scenes developments in the lead up to Thatcher's tearful exit from Downing Street on November 22, 1990.
"Henry Kissinger telephoned me in a very emotional state about your decision to resign; it was worse than a death in the family," Thatcher's private secretary, Charles Powell, wrote in a note.
In reference to Gorbachev, Powell described an "unusually warm and friendly" letter addressed to "Margaret" expressing his appreciation for the "mutual understanding" they had established.
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"Gorbachev had sent Shevardnadze (his foreign minister) out of a high-level meeting in the Kremlin to telephone him, to find out what on earth was going on and how such a thing could be conceivable. The ambassador said that he had indeed found it very hard to explain.
"Indeed, there was a certain irony. Five years ago they had party coups in the Soviet Union and elections in Britain. Now it seemed to be the other way round," Powell wrote.
Thatcher had been forced to step down after her own Conservative party colleagues turned against her and Michael Heseltine launched a leadership challenge.
She was succeeded by John Major, who fought off other contenders in the infighting.
Other files released by the National Archives include UK Cabinet files for 1989 and 1990 which include the minutes of Thatcher's last Cabinet meeting and a notification for Downing Street to register for its poll tax, the controversial levy linked to Thatcher's eventual resignation.
The files also disclosed that while Thatcher was reported to have a "chilly relationship" with Queen Elizabeth II, she enjoyed a secret friendship with the Queen's sister - Princess Margaret.
Handwritten notes sent between them at the beginning of 1980 were laden with compliments as the pair discussed topical issues, from Afghanistan to the steel industry.
Thatcher praised the royal for her "wonderfully successful" tour of the United States, as she revealed she was "very distressed" to hear she had been admitted to hospital again.
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