Yet, as final preparations are made for the Mandela concert in Hyde Park, thousands of miles away another African former "freedom fighter" continues to bring his country to its knees. After 28 years of repression, Robert Mugabe's determination to defy the will of his own people and that of the world shows no sign of wavering. If anything, he has become more despotic since he lost the first presidential election to the Movement of Democratic Change's (MDC) Morgan Tsvangirai on March 29. With a run-off ballot due next weekend, Mugabe last week insisted "only God" could remove him from power.

Perhaps Mugabe's most sinister proclamation was his warning to voters: "How can a pen fight a gun?" He was merely stating his Zanu-PF government's official policy: the MDC claims at least 70 of its supporters have been killed since the first ballot; a group of Zimbabwean medics put the toll higher on Friday, releasing a list of 85 people who had died as a result of political violence, 21 of them executed after being snatched from their homes or off the streets; Tsvangirai himself has been detained five times while campaigning, and the MDC's secretary-general, Tendai Biti, remains in custody on treason charges; yesterday, television pictures showed stick-wielding Zanu-PF supporters beating up people to make sure they vote the right way next week. Mugabe was unmoved, insisting all such claims were a "damn lie" put about by the MDC to undermine the elections.

Here in Britain, Gordon Brown and David Miliband have been outspoken on the plight of Zimbabwe, in turn incurring the wrath of Mugabe, who sees all British input as an attempt to revive a colonial past. The British Government is right to ignore such nonsense and keep up the pressure for change. But if Zimbabwe is to be freed from the grip of this brutal dictator then greater efforts will have to come from closer to home.

Until recently, too many African leaders have been prepared to turn a blind eye to the iniquitous behaviour of their neighbour. But that appears to be changing, especially among those nations which have seen four million Zimbabwean refugees flood across their borders – and are braced for millions more if Mugabe engineers events to make sure he stays in power. Seretse Ian Khama, the newly elected president of Botswana, was the first to protest against Mugabe's violence towards his own people. Zambian president Levy Mwanawasa, Tanzanian president Jakaya Kikwete and Kenyan prime minister Raila Odinga have added their own words of criticism.

The glaring omission is the most powerful neighbour of all, South Africa. The man who now holds Mandela's old job as president of South Africa, Thabo Mbeki, has stuck by a policy of encouraging mediation long after outright condemnation of Mugabe would seem to be the appropriate response. Last week he urged Mugabe to cancel the run-off ballot and form a government of national unity. He should instead have withdrawn his support from the dictator and threatened sanctions, including the loss of vital power supplies, unless he steps aside.

And where is the United Nations? Aid organisations and media groups have been banned from Zimbabwe, but enough evidence exists for the UN to take action. Too many countries are profiting from the hell that is Zimbabwe under Mugabe. The UN must act now before this blighted country gets even worse.

The world must not underestimate the potential for a bloodbath that would stain Africa for decades to come. With many African leaders finally voicing their anger, it is time for a concerted international effort to oust Mugabe. It would help immensely if Mandela used his own birthday celebration in London to add his powerful voice to the growing swell of opinion. Then, at last, South Africa might be forced to act and help save Zimbabwe.