At the beginning of this week of horrors, Nelson Mandela at 85 made his farewell speech to parliament in Cape Town, commemorating 10 years of democracy in South Africa, before retreating from public life.

At the beginning of this week of horrors, Nelson Mandela at 85 made his farewell speech to parliament in Cape Town, commemorating 10 years of democracy in South Africa, before retreating from public life.

He looked back at his experience in peacemaking in his own country. "Historical enemies succeeded in negotiating a peaceful transition from apartheid to democracy exactly because they were prepared to accept the inherent capacity of goodness in the other."

And he went on to make his strongest criticism yet of American and British policies in the Middle East. "We watch as two of the leading democracies ... get involved in a war that the UN did not sanction: we look on with horror as reports surface of terrible abuses against the dignity of human beings held captive by invading forces in their own country."

It was one of the most important speeches of Mandela's career since his statement to court in 1964, before he was sentenced to life imprisonment, and it summed up his political attitudes which are now of pressing relevance to the world.

Respecting other people's dignity, and avoiding humiliation, had been the key to Mandela's peacemaking, whether in dealing with warders during his years in jail or in negotiating afterwards with Afrikaner government ministers. And he was now seeing images from Iraq which showed the deliberate humiliating and degrading of prisoners, and watching both sides' escalating reprisals, with a mounting rhetoric of evil and hatred.

Mandela's speech was not shown on British television. Instead, on the same day, Channel 4 chose to air at prime time, with much publicity, a documentary, Beneath the Halo, in which the right-wing commentator Peter Hitchens set out to debunk the image of Mandela as a saint, and to show - with misleading evidence - that South Africa under Mandela and his successor Thabo Mbeki had degenerated into poverty, crime and incipient chaos.

It was a deliberately provocative programme, on the pattern of an earlier debunk of Mother Teresa by the commentator's brother Chris Hitchens, which had achieved the notoriety it sought. It dwelt on criticisms of Mandela and the ANC, and sought to prove that Mandela, as Hitchens said, was "a fig leaf for a government which was nothing like as nice as he is".

But it was based on a quite false assumption: that Mandela and his party had set out to establish his saintliness. In fact it was the outside world that chose to put him on a pedestal - particularly Conservatives who were thankful to be forgiven, after so often attacking him in the past.

Mandela had emphasised to me, when I wrote his authorised biography, that he was worried in his last years in jail by the world's image of him as a superman: he wanted to be depicted as an ordinary man, not a saint. His achievement depended on his being a master politician who understood "the art of the possible" and who realised that he must always carry his people with him. And he knew his human failings. A saint he ain't.

Before the programme was screened, the South African government wrote to the head of Channel 4, Mark Thompson (now a candidate to be director general of the BBC), seeking an opportunity to present a balanced viewpoint. But Thompson replied in patronising prose that "you can rest assured that the appropriate approaches were made" to ministers. He was satisfied that the programme "has been made in a fair and responsible way".

It was hard to see the eventual product as "fair and responsible". I had reluctantly agreed to be interviewed for it, having been assured that it would "look at the crucial role Nelson Mandela has played". I tried repeatedly to contradict the hypothesis, explaining how Mandela never wanted to be depicted as a saint. But the programme included only my one criticism: that he was too slow to respond to the catastrophe of Aids.

In normal times, such a programme would not be worth mentioning. It could be seen as just another step in the vulgarisation of Channel 4, a victory of entertainment over information. It might even have been justified as a corrective to the past hero-worship of Mandela - provided it was followed by some balance from the other side.

But at a time of international crisis, when British television desperately needs serious coverage of current affairs, it is noteworthy that Channel 4 should offer a provocative and one-sided debunk of a major world leader with an important message.

At no point did the programme show Mandela explaining the argument behind his "crucial role" which he has so often made: that peacemaking depends on recognising the dignity and goodness of people on the opposite side - an argument that is now urgently important to make to both sides across the dangerous Middle Eastern divide.

It was Mandela's emphasis on mutual understanding, and his own transformation of his country into a multiracial democracy, which led protagonists elsewhere, including Northern Ireland and the Middle East, to look to South Africa as a model, and encouraged world leaders including Blair and Clinton to welcome him as a saviour - though not a saint. They had their own reasons to enjoy his reflected glory, but they knew that Mandela had a moral authority which no other contemporary leader could claim.

Blair's interest in Mandela diminished as he was determined to oppose the Iraq war from the beginning. He attacked both Britain and America for breaking international law. He argued personally with Blair, as he told me, to remind him of the indispensable role of the UN.

Mandela's long historical experience and perspective are much more important, as both Blair and Bush are under fire after the revelations of torture and abuses of prisoners, and while both sides in the Middle East accuse the other of worsening atrocities and brutality.

The pattern of escalating horrors and reprisals is all too familiar to anyone who has lived through previous hideous wars, from the Mau Mau rebellion in Kenya to the Algerian war to the Vietnam disaster - which all ended in the virtual capitulation of the West.

The same escalation appeared inevitable in South Africa, with the same demonisation of the enemy, and the same atrocities and tortures which brutalised the perpetrators. The disaster was averted by the wisdom of Mandela and de Klerk, who were prepared to realise that there was humanity and good sense on the other side, and who prepared the way for a unique multiracial settlement.

It was Mandela's ability to see beyond the bitterness and hatred, and to reconcile with his enemies, which makes his message so invaluable to the rest of the world today. And he is one of the few leaders who can command equal respect on both sides of the Middle East divide, with friendships with Islamic as well as Christian leaders.

How much more serious does the world crisis have to become, before our media accept responsibility to present viewers and readers with a balanced picture of the real issues that lie behind it?