What was surprising was the harsh tone which accompanied the change - with an uncompromising stream of attacks on whites, "white parties" and the "white-owned media" - and the fact that the warm and cuddly President Mandela, not Thabo Mbeki, his much-vilified successor, used his last speech as party leader to lead the scathing, and for him unprecedented, assault.
Could this be the same man that took tea with Betsy Verwoerd, ageing widow of the architect of apartheid - a reconciliation too far in the eyes of some party members? Coming from President Mandela the change in tone could not have been more stark. At first it was assumed that while it was Mr Mandela's lips that were moving Mr Mbeki, sitting a few feet away, was, ventriloquist-style, doing the talking.
At every turn, according to President Mandela, the ANC was being thwarted by those "committed to the maintenance of white privilege". The proceedings of the Truth and Reconciliation Commission, the body charged with exposing the atrocities of the apartheid years, showed "the unwillingness of white society in general, including white politicians, business, the judiciary, the media and the church, to explain its involvement in the maintenance and perpetuation of the apartheid system".
That betrayed white society's hostility to the new democratic South Africa, he argued. Mr Mandela has spent a large part of his presidency wooing truculent right-wing Afrikaners to the new political dispensation. But yesterday he had harsh words for them too. "They [Afrikaners] continue to be imprisoned by notions of white supremacy and of supposed Afrikaner interests that are separate and opposed to the interests of the rest of the population."
Faced with deep divisions within the ANC, the president sought to blame everything from crime to the slow pace of social change on white resistance. He labelled the opposition National Party and Democratic Party "reactionaries", dedicated to preserving white privilege. But he reserved his most scathing comments for the white-owned media - a source of irritation to the president from time to time but Mr Mbeki's enduring pet hate.
The media, he insisted, were deliberately trying to undermine the ANC revolution. "During the last three years it has become perfectly clear that the bulk of the mass media in our country has set itself up as a force opposed to the ANC."
He seemed irritated by the press's desire for a real opposition to the ANC to emerge. He said the media, like white parties, were wrong in portraying South Africa as a mature democracy. "We are still involved in the delicate process of nursing the new-born baby into a state of adulthood," he said. Some might have remembered, with a shudder, the early years of independence in Zimbabwe, South Africa's northern neighbour. Robert Mugabe, then internationally popular, described the foundations of democracy as luxuries a new country could not afford.
The onslaught on the press resurrected the spectre of a future "independent" regulatory body for the media which might pronounce on everything from what is newsworthy to what constitutes public interest. Close associates of Mr Mbeki have been floating that kite for months. Last week, Mr Mbeki again raised the idea of government information bulletins being broadcast on national television.
None of these suggestions has been embraced by the media. Mr Mandela said yesterday that in order to protect privileges which found their roots in the apartheid era, the media denounced "all efforts to ensure its own transformation ... as an attack on press freedom".
The attacks on the press and on whites were loudly applauded by the thousands of ANC delegates who travelled to Mafikeng in the North-west province yesterday for the first day of a five-day conference. Under apartheid, the press was the mouthpiece of the enemy. Yesterday, that still seemed to be pretty much the view.
Most delegates thought the president had got the tone just right. "The last conference in 1994 was about reconciliation but this is about our country's transformation," said one female delegate.
So was Mr Mandela speaking for himself or Mr Mbeki? One black commentator said: "It needed to be said and he had to say it. If Mbeki had said it he would have been vilified just as he is about to take over."
But he added that the speech came from a frustrated presidential heart. Three years on, the president was dismayed at white indifference in redressing past injustices. "He has been saying these things for months in private," said the commentator.
But the president was surely trying also to satisfy disillusioned elements in the party. In its 85-year history, the ANC has probably never been more divided. Three years after taking power it has yet to transform itself from broad-church revolutionary movement to political party.
Winnie Madikizela-Mandela, the president's former wife, shared the platform with him and the ANC executive yesterday. Almost seated in the wings, she could not have been placed further from her ex-husband.
Mrs Mandela, accused during TRC hearings of involvement in eight murders, is expected to seek nomination this week, despite the ANC leadership's best efforts, for the ANC deputy presidency. Her attacks on a leadership - considered far from radical by the grassroots - have struck a chord in some quarters.
After Mr Mandela's speech his former wife joined the queue of wellwishers to offer congratulations. Nelson and Winnie smiled broadly as they embraced briefly but warmly amid crowds of supporters who sang and danced around them.