In a break with custom, the eight members of the world's most exclusive club each appended their signature to what they had agreed. In doing so they expanded the previously limited horizons of the G8 with regard to the poorest people of our world, the bulk of whom live in Africa, a continent a mere 8 miles from Europe at its nearest point.

Gleneagles agreed to implement 50 of the 90 recommendations made by the Commission for Africa set up by Tony Blair to analyse a way out of the African malaise. In Gleneagles, the G8 proposed deals on debt cancellation and aid (an extra $25bn (£14bn) a year for Africa) far more significant than anyone could have imagined a year ago.

Even though trade is not normally on the G8 agenda - it is dealt with through world trade talks, the next round of which takes place in December in Hong Kong - at Gleneagles the G8 did recognise, for the first time, that rich nations should not force economic prescriptions on poor countries. And it made an important committment to building Africa's infrastructure and capacity to trade - a problem which the Commission found was as serious an impediment for Africa as rich nations' trade barriers. Regrettably, despite a last-minute flurry of lobbying, the G8 did not offer the deal we wanted to end the way rich countries subsidise their agricultural exports and thus harm farmers in poor countries. That and other battles must now wait until Hong Kong in December.

But the most immediate task is to put back on track progress towards the halving of world poverty by 2015 - as agreed at the UN summit of 2000 and captured in the Millennium Development Goals (MDGs). On present trends the target for the reduction of child deaths by 2015 will not be reached until 2115. Such is the awful cynicism that can lie behind the solemn "binding" word of so many political documents.

The package proposed by the Commission, and backed at Gleneagles outlined a way to put the MDGs back on track, particularly with regard to Africa. But it must now be implemented aggressively if it is to live up to its historic implications.

Those of us involved with the Commission for Africa, Live 8 and the Gleneagles summit always knew it would be a long incremental process. The Commission was completed, Live 8 achieved, Gleneagles signed. But now we must try to ensure that today's UN summit places poverty at the very centre of its focus. The African bloc at the UN have a critical role to play in making this so. Other matters cannot be allowed to sidetrack us from this most important of world issues. It is imperative that the commitments made at Gleneagles are affirmed through the UN, and activated, paid for, and followed up in their entirety.

The Commission for Africa called for a small monitoring group to report on the progress of this implementation. Prior to the summer break I spoke with the Prime Minister who agreed to its necessity. Hopefully a small credible group - with a built-in lifespan of perhaps five years, representing both Africa and the developed world, and with serious political clout, independence and teeth - can be constructed soon to do that.

There is much to do to lift the poor, sick, powerless and uneducated out of their miserable conditions. I'd like to see the Commission's aid deal delivered by the earlier date of 2008, not the later one of 2010. The Dutch and Belgians must stop trying to dismantle the debt deal, which must not be delayed beyond next week's meetings of the IMF and World Bank, nor used as a backdoor means to pile on conditions.

The world has become impossibly Dickensian. We no longer wear top hats nor carry canes but we still swerve around the bodies of the ill and dying in the midst of plenty. Everything that has happened in the past year - the Commission for Africa, Make Poverty History, Live 8, the Gleneagles G8 and now the UN summit - has been designed to try to bridge the gap between those two worlds. It has been, within our limited terms of reference, a success but it is not nearly adequate. The task before global anti-poverty campaigners is to hold our governments accountable, accelerate delivery, and support improvements, especially on trade. And if the G8 break their solemn pledges to the poor, there must be a reckoning.

We must not be distracted from aggressive implementation by side arguments or internal squabbling. I am almost frightened by the urgency of this task.