As she did in life, Margaret Thatcher continued to divide politics in Northern Ireland on Monday following her death at the age of 87.
Britain's only female Prime Minister passed away peacefully after suffering a stroke, having battled poor health for a decade.
A grocer's daughter from Grantham in Lincolnshire, Baroness Thatcher became the UK's longest serving premier of the 20th century.
By the time she left office in November 1990 she had changed the face of the country.
She will be given a full ceremonial funeral at St Paul's Cathedral next week.
Prime Minister David Cameron led tributes from around the world, describing Baroness Thatcher as "a great Prime Minister, a great leader, a great Briton".
In Northern Ireland, First Minister Peter Robinson paid tribute to a "transformative and powerful" woman who "entered politics to make a difference".
"She was undoubtedly one of the greatest political figures of post-war Britain and she changed the face of our United Kingdom for ever," Mr Robinson said.
But Sinn Fein president Gerry Adams reacted with a scathing assessment of her political legacy in Ireland and elsewhere.
"Margaret Thatcher did great hurt to the Irish and British people during her time as British Prime Minister," he said.
"Here in Ireland her espousal of old Draconian militaristic policies prolonged the war and caused great suffering."
Elsewhere, cheering people held parties to "celebrate" the death of Baroness Thatcher.
A crowd of two or three hundred people assembled in Glasgow's George Square where in 1989 protests to the introduction of Thatcher's poll tax took place.
And in Londonderry, crowds gathered at Free Derry corner to light Chinese lanterns and wave the Irish tricolour and dissident republican flags.
Baroness Thatcher died at 11am on Monday at the Ritz in London, where she had been staying since January following a minor operation.
The Union flags above Downing Street, Buckingham Palace, Hillsborough Castle and many other landmarks were lowered to half-mast.
Known as the Iron Lady, she served 11 unbroken years at No.10 before being overthrown in a Tory party coup in 1990.
Her term as Prime Minister spanned some of the most tumultuous years of peacetime Britain.
She defied miners' leader Arthur Scargill, defeating his nationwide and year-long strike over pit closures.
Perhaps the defining point of her premiership came when Argentina invaded the Falkland Islands in April 1982. The resulting conflict lasted 74 days, ending with the Argentine surrender and the islands' return to British control.
But she won few friends in Ireland with her unwavering belief in the Union.
Her handling of the hunger strikes turned her into a hate figure for much of the nationalist community.
She narrowly survived the 1984 Brighton bombing which almost wiped out the Government. Five people died and many others, including Cabinet Minister Norman Tebbit, were seriously injured.
However, by late 1990 her fortunes had plummeted, capped by a series of damaging resignations from the Cabinet.
She famously left Downing Street in tears, sobbing in the back of a limousine as her years of power ended.
Prime Minister David Cameron cut short his trip to Europe to return to London, where he hailed the lasting legacy of a "great Briton" who defied barriers.
Mr Cameron said Parliament would be recalled on Tuesday for MPs to pay tribute.
Buckingham Palace said The Queen was "sad to hear the news of the death of Baroness Thatcher".
US President Barack Obama said the world had "lost one of the great champions of freedom and liberty, and America has lost a true friend".
In Northern Ireland the Assembly held a special half-hour session with tributes but the Speaker, William Hay, had to demand order several times as Sinn Fein's Raymond McCartney read Mr Adams' statement.