The BBC read out a statement from Thatcher's friend and former advisor, Tim Bell, saying: "It is with great sadness that Mark and Carol Thatcher announce that their mother, Baroness Thatcher, died peacefully following a stroke this morning."
In nearly a dozen years as Britain's leader, beginning in 1979, Thatcher transformed its political and economic landscape through a conservative free-market revolution bearing her name, Thatcherism, which sought to reverse the country's postwar decline and the welfare state that she felt accelerated it.
• Lord Bell's statement announcing Lady Thatcher's death
• Margaret Thatcher – obituary
• Margaret Thatcher: a life in pictures
• Margaret Thatcher's Britain - an interactive presentation
• The life of Margaret Thatcher – timeline
President Obama has released his tribute. Here it is in full.
"With the passing of Baroness Margaret Thatcher, the world has lost one of the great champions of freedom and liberty, and America has lost a true friend. As a grocer’s daughter who rose to become Britain’s first female prime minister, she stands as an example to our daughters that there is no glass ceiling that can’t be shattered.
As prime minister, she helped restore the confidence and pride that has always been the hallmark of Britain at its best. And as an unapologetic supporter of our transatlantic alliance, she knew that with strength and resolve we could win the Cold War and extend freedom’s promise.
Here in America, many of us will never forget her standing shoulder to shoulder with President Reagan, reminding the world that we are not simply carried along by the currents of history—we can shape them with moral conviction, unyielding courage and iron will.