The events of this week mark a milestone in Zimbabwe's history. The Harare agreement is a breakthrough that represents the country's last, best chance of averting apocalypse. Sceptics insist that the deal cannot work; but for millions of suffering Zimbabweans, it is a sweet tea. And the risk is now that the international community might inadvertently undermine this source of hope.
It will not be easy to make this deal work; and MDC leader Morgan Tsvangirai, Zimbabwe's new prime minister, has no illusions about the size of the task facing him. In yesterday's Guardian interview he spoke of the "inherent suspicion" between the reluctant partners. He also pointed out that not only would he have to handle Robert Mugabe and the Zanu-PF, but that he might also face opposition from MDC hardliners who want no truck with the Zanu-PF elite.
Tsvangirai will also have to gain the respect of the generals, without becoming one of them. Sooner or later, though he will have to make a decision on whether to persuade the military top brass to stand down, or order them to do so. A clash between Tsvangirai and the military is looming, and how he handles it will be essential to his political survival. His other immediate priorities will be to bring food, water, sanitation and medicine to the people; reforming the Reserve Bank of Zimbabwe; and repealing repressive legislation.
The role of the international community is crucial to the survival of the new unity government, and there is an expectation that the MDC can deliver on foreign investment. But so far the European Union, the United States, the World Bank and International Monetary Fund have given a tepid welcome to the deal, and have stated that the new government must "prove itself".
What they really mean is that they are upset Mugabe is still in the picture, and they will not provide aid until Tsvangirai ousts him. Although this response is not unexpected given the decade of hostility between the west and Zanu-PF, it is wrong. The west has to abandon this orthodoxy of demonisation, which ignores the obvious. First, without aid, Zimbabwe will die. Second, the goalposts of Zimbabwe's politics have irrevocably shifted. Although the agreement is notionally about power-sharing, in reality it sets the seal on the transition of power. The process will be lengthy, and fractious, but there can be no going back: Zimbabwe is entering a new era of leadership. Third, Tsvangirai and the MDC have already "proved" themselves - and they carry the scars of struggle to prove this.
Without donor aid, the Harare agreement will become merely a political armistice, a brief interlude in Zimbabwe's civil war. If Tsvangirai is unable to persuade the donors to unlock their vaults, his usefulness - and shelf-life - will be brief. Failure by the international community to recognise the new government, and make at least a symbolic investment, would be to misinterpret Zimbabwean realpolitik and could only be destructive. Mugabe remains a major part of Zimbabwe's political landscape. His time is passing, but he cannot be wished away - and Zanu-PF still holds the knife by the handle.
Tsvangirai, and in turn the Zimbabwean people, should not be punished for signing a deal with Mugabe. Western governments are right to worry about continued violence and corruption in Zimbabwe, and they cannot dispense aid willy-nilly, especially during this economic downturn. But the country needs aid, and it needs it now.
The west and Zanu-PF will also have to re-establish a relationship. Driving Mugabe underground will only encourage a lethal Zanu-PF unilateralism. Travel sanctions on the Zanu-PF elite will remain in force, but there is no reason why meetings cannot be held in Zimbabwe, or on neutral territory. Just as Zanu-PF and the MDC have formed a government of national unity, so too does the international community have to take an inclusive, not sectarian approach to Zimbabwe's politics of reconstruction. Zanu-PF, in turn, must demonstrate that it is no longer addicted to violence.
Britain and Zimbabwe do have a "special relationship": to pretend otherwise is facile. The relationship has often been acrimonious, and it is laden with a deep mistrust about the colonial past and recent history; but it can be salvaged and reformulated in ways that are mutually beneficial and not exploitative.
None of the signatories to this agreement got everything they wanted, but Zimbabweans got what we needed: hope. It is ordinary Zimbabweans of all races, not the political elite, who will have to empower the agreement for it to work. After years of blood, sweat and tears, Zimbabwe finally has a deal - but we will need the world's help to give peace a chance.
Knox Chitiyo, head of the Africa programme at the Royal United Services Institute, London, and a former co-director of the Centre for Defence Studies at the University of Zimbabwe.