When this century is at its end, will the UN Millennium Summit be seen as a historic event inaugurating a new era of international peace and prosperity, or will it be just another showy but meaningless gathering like all those sessions of its predecessor, the League of Nations, which failed to prevent the second World War?

The answer, like the Chinese leader Zhou Enlai's comment about the impact of the French Revolution, is that it is too early to say. The fact that the event took place at all and was so well-attended showed that the governments of the world still felt obliged to pay lip-service, at least, to the UN, and believed there was some benefit in making the trip to New York.

Nations both great and small were represented. Abiding memories include President Clinton's 32-car motorcade rolling through the streets of Manhattan like some enormous and terrifying juggernaut in a disaster movie and, at the other end of the scale, the curiously moving sight of the delegation from Tuvalu in the Western Pacific, the UN's newest member-state with a population of 10,000, arriving for an official meeting.

The artist Andy Warhol said everyone got 15 minutes of fame, but with some 150 heads of state or government on hand, each speaker only got five minutes at the General Assembly. Everyone got the same time, regardless of their real political weight on the world stage.

UN headquarters itself, a delight to the eye in its spectacular setting beside Manhattan's East River, has a strangely old-fashioned atmosphere inside. It brought back memories of a stay some years back in the former Intercontinental Hotel in Tehran, a state of the art building under the Shah but effectively frozen in time since the Islamic revolution. The seating for visitors and the press in the General Assembly needed upgrading, the earpieces for listening to speeches required exceptional powers of hearing and the press canteen on the third floor was like a works caff in Sunderland in the 1950s.

You do not need to see the accounts to surmise that this organisation needs a serious cash injection, not just at headquarters but, more generally, in its many and wide-ranging activities covering almost every sphere of human life.

As so often at these events, the process had a production-line feel about it. Television monitors showed speaker after speaker, whether in the flowing attire of an Arab prince or the well-pressed suit of a western prime minister, reciting their thoughts to their fellow statesmen and women.

But in the hustle and bustle of the corridors and the press room, hardly anyone seemed to be listening and there was only a handful in the visitors' gallery of the Assembly itself.

It was a somewhat misleading impression, of course. And important things were happening, in the French diplomatic phrase, en marge. For example, the casual and possibly accidental encounter between Bill Clinton and Fidel Castro broke the ice between the two countries after 40 years of a sub-zero relationship.

The significance of this event can be gauged by imagining the delight there would be in many quarters at home if David Trimble and Gerry Adams were at long last to shake hands in a gesture of peace and reconciliation.

Ireland attracted attention with the Taoiseach's solemn commitment to meet the UN target on overseas development aid by 2007, involving a quadruple increase from £200 million to more than £800 million over a seven-year period.

Even if Bertie Ahern has moved on before then, the undertaking will remain on the record and there will be a strong moral imperative to fulfil it.

Ireland's campaign for a Security Council seat got a boost from the Taoiseach's speech and a gruelling canvass he conducted among the delegations. These activities were conducted with a nervous glance over the shoulder for the Italians - probably our main rivals - lest they should discover whom the Taoiseach was meeting and apply their formidable skills and endless charm to win them around.

The event was not all solemn speeches and sombre statistics. There was a lighter moment when a UN photograph of the world leaders turned out to have more than the official tally. Shades of the Woody Allen film, Zelig, it was said that tiny San Marino had got two of its representatives into the frame, instead of one, and the other face was reported by the New York Times to be Count Carlo Marullo di Condojanni of the Sovereign Military Order of Malta.

Naturally, the eight-page declaration adopted by the world leaders at the end was going to contain a great deal of "motherhood and apple pie", but it could be argued that at least concrete and specific aims had been agreed and success or failure could be measured against these targets in due course.

As the UN Secretary-General, Mr Kofi Annan, stated at the beginning of the summit, while the problems seemed huge, "in today's world, given the technology and the resources around, we have the means to tackle them. If we have the will, we can deal with them".

The year 2015 is a recurring date on the list of UN targets. Russia's President Vladimir Putin suggested that a follow-up summit - along the lines of last week's event - should be held again.

Perhaps, therefore, 2015 would be a suitable moment to look back and see what has been achieved.