A Ghanaian, Annan will be the first black African to lead the organisation. And he will be the first international civil servant to do so. He has in total spent 30 years inside the UN system. That would usually mean the death of a man's reputation and of his soul. Not in the case of Annan. Both seem still to sparkle.
The other candidates were politicians with greater or lesser management skills. Annan is a manager with political skills. He has a proven track record as a negotiator and conciliator. He is a known quantity to both the staff and to member nations. With both he enjoys great popularity.
He is very different from the man he replaces. Boutros Boutros-Ghali carried out far more reforms in the UN than the United States gave him credit for. But his patrician manner, and his management style - he once said that he administered "by stealth and sudden violence" - did not endear him to staff.
Annan, by contrast, has a gentle personality but a quick sense of judgement and a determination not be diverted. Some diplomats circle round problems, hoping they can be evaded. Annan deals with them straight on but not in a confrontational manner. His staff love working for him.
He has a wicked sense of humour. Knowing that the French insist that any leader of the UN must speak fluent French, he joked recently, "I now speak English with a French accent". He smiles a great deal but he has quiet dignity and although he is, he says, a team player, he does not waver or weaken.
He has simple tastes. He and his Swedish wife, Nane, a distinguished painter, have lived till now a quiet and unassuming life on Roosevelt Island in the East River. They ate in modest restaurants and Annan was to be seen of an evening leaping up the steps on 62nd Street and 2nd Avenue to catch the cable car. Nane's studio was in an old warehouse in Queens, with a view across the river to the UN building.
Now most of that will have to be swapped for a sumptuous house on Sutton Place, one of the best addresses in New York, bodyguards and chauffeurs. Now he has the almost impossible job of restoring the UN's finances and reputation.
It is really two jobs - administering one of the most politically sensitive, not to say neurotic, bureaucracies in the world, and providing the world with moral leadership. It would not be surprising if Annan looked to the example of Dag Hammarskjold, Nane's compatriot, who brought great moral authority to the UN at the height of the Cold War in the 1950s. Brian Urquhart, the dean of UN officials, points that while Annan shares Hammarskjold's devotion to the UN charter, he lacks the Swede's mystical individualism. "But he really does believe in what he is doing. He's not an egomaniac. He's a genuine public servant. It's very refreshing."
KOFI ANNAN is from a family of traditional chiefs of the Fante tribe. He grew up in Ghana and won a Ford Foundation scholarship to Macalester college, Minnesota, at the end of the 1950s. He then did postgraduate economics in Geneva and earned a master of science degree in management at the Massachusetts Institute of Technology.
Since 1962, he has worked for the UN: for the High Commissioner of Refugees and the World Health Organisation, in Geneva, Addis Ababa, Cairo and Ismalia, before joining the UN secretariat in New York. Not many bureaucrats come through any bureaucracy with ever increasing pop- ularity, but Annan has done so.
When he was sent to former Yugoslavia in November 1995 to hand over the UN operation to Nato after the Dayton Peace Agreement, he was already spoken of as an alternative to Boutros-Ghali. Some thought that the Secretary General was therefore handing him a poisoned chalice. His predecessor, Yasushi Akashi, had seen the fine reputation he had won in the peacekeeping operation in Cambodia badly damaged in the Balkans.
Not Annan. His style, more direct than Akashi's, won him praise, even among the diverse factions in the Balkans.
On a rainy evening in November 1995, I went with Annan to the Serbian suburb of Grbavice. The mayor, Milorad Katic, told Annan that the Dayton plan was unacceptable to the Serbs of Sarajevo. It must be renegotiated.
Annan was unequivocal, while appearing sympathetic. He replied, "I have to be frank with you. Dayton was a compromise. But it was signed by the heads of state and it is not negotiable. What is important is that it should be implemented fairly. Don't try to reopen Dayton but work for its implementation. You should let the world hear you - that you want to live in peace."
That same evening, Annan visited the headquarters of the French battalion in Sarajevo. He did what he could to cheer them, a task he sees as paramount.
"Don't be discouraged by media critics," he said. "Unprofor has done very well. Virtues always go elsewhere. Defeats stay with the peacekeepers."
In March this year I accompanied Annan on his farewell tour of former Yugoslavia. When he flew to Belgrade, he brought with him a cheque for $1m and an agreement worked out between the UN and Yugoslav government that this was in full, final compensation for damage to an army barracks allegedly done by French troops with the UN.
Outside the Prime Minister's office Annan was told that the army wanted another $300,000. This would mean reopening the whole negotiation. Quietly but forcefully, and with a smile, Annan told the Prime Minister that he hoped he could leave the cheque and settle the whole matter before he left that day. He made it clear that renegotiation was not on. In the end the Prime Minister ordered the Minister of Defence to sign for the cheque - and so to take the heat from the army. Annan won.
His farewell week was spoilt by a UN tragedy that epitomised the crisis of the world organisation. Iouri Myakotnykh, a jovial former Soviet ambassador, was a gifted senior UN official. He had previously been one of Moscow's top Indochina experts. I knew him as Russian ambassador in Cambodia, where his diplomatic skills, knowledge and good humour had been vital in securing the UN peace process.
Myakotnykh drove from Belgrade to meet Annan in Zagreb. Just as he was nearing the Croatian capital he fell asleep at the wheel. His car crashed and he died instantly. His colleagues were furious that the UN had not provided him with a driver. The financial crisis was blamed.
Annan was devastated by the news and spent the next few days visiting his colleague's wife, talking to shocked staff in Belgrade and trying to arrange the most generous treatment for Myakotnykh's family.
More than 200 UN officials died or were killed during the often vilified UN peacekeeping operation in former Yugoslavia. Annan argues that much of the criticism of the UN Protection Force by governments (especially Washington) and the press has been misguided. It should instead have been levelled at the Security Council which set the peacekeepers impossible mandates and gave them inadequate resources to carry them out.
Some diplomats at the UN have suggested Annan may be just too nice to enforce the radical reforms the UN needs. But he is no one's poodle. When the Clinton administration withdrew troops from Somalia after the death of American soldiers there in 1993, he said that "the impression has been created that the easiest way to disrupt a peacekeeping operation is to kill Americans". And in 1994 he upset African ambassadors when he told the French newspaper Le Monde that it was difficult to recruit African troops for peacekeeping missions because their governments "probably need their armies to intimidate their own populations".
BOUTROS-GHALI had to go, said American officials, if only because the Republican-dominated US Congress distrusted him and would not fund the UN so long as he stayed. Does Annan have a better chance of convincing the US to pay its $14bn debts? Yes.
But changing the pilot will not by itself change the direction of the organisation. That can be done only by the member states, in particular the five Security Council members. Since the end of the Cold War there has been no consensus on what the UN is for and what it should do. It will be Annan's supreme task, with the member states, to create such a bold consensus. Not easy.
Privacy and the modest lifestyle Annan and his wife have enjoyed till now are gone. Annan belongs to the world for the next five years. It is my belief that the world will be a better place as a result.