Baroness Thatcher has died at the age of 87 following a stroke, her family has announced.
As tributes poured in to the former premier, it was announced that she will receive a ceremonial funeral with military honours at St Paul's Cathedral. Downing Street gave details of the event after the Tory former prime minister died on Monday morning. She had been in ill health for several years and was rarely seen in public in recent years.
The Queen was said to be "sad" at news of her death and Prime Minister David Cameron praised her as a "great leader" and a "great Briton". Liberal Democrat leader Nick Clegg said Mrs Thatcher had been one of the "defining figures in modern British politics".
The "world has lost one of the great champions of freedom and liberty, and America has lost a true friend" following Baroness Thatcher's death, US President Barack Obama said.
A Number 10 spokesman said: "We can announce that, with the Queen's consent, Lady Thatcher will receive a ceremonial funeral with military honours. The service will be held at St Paul's Cathedral. A wide and diverse range of people and groups with connections to Lady Thatcher will be invited. The service will be followed by a private cremation. All the arrangements being put in place are in line with wishes of Lady Thatcher's family. Further details will be published over the coming days."
Mr Cameron is returning early from an official trip to Spain after the news of Baroness Thatcher's death was announced by her spokesman, Lord Bell. She is understood to have been recuperating at the Ritz Hotel in London after a minor operation.
Baroness Thatcher earned a place in the history books as the first woman prime minister when she entered Downing Street in 1979. Over the next 11 years even her critics admitted that she changed the face of the country.
She suffered several small strokes in 2002, and received medical advice against accepting any more public speaking engagements. Her increasingly frail condition when she was seen - especially after the death of husband, Denis, in 2003 - led to frequent bouts of speculation about her health. But MPs and friends who saw her regularly said she remained alert and interested in politics.
Labour leader Ed Miliband said: "I send my deep condolences to Lady Thatcher's family, in particular Mark and Carol Thatcher. She will be remembered as a unique figure. She reshaped the politics of a whole generation. The Labour Party disagreed with much of what she did and she will always remain a controversial figure. But we can disagree and also greatly respect her political achievements and her personal strength."
It is understood that Lady Thatcher was consulted about details of the funeral arrangements, and made clear that she did not want her body to lie in state. The streets between Westminster and St Paul's will be cleared for the procession, the date of which is yet to be decided. It will not be a formal state funeral. The flag at Downing Street was lowered to half-mast in tribute today, while parties were suspending campaigning for local elections out of respect.