IT is perhaps only once in a lifetime or even in a generation that a calamity occurs of such colossal and earth-shaking proportions that it stops us in our tracks.

A calamity that impresses on us most suddenly and dramatically what not to take for granted, one that reminds us of destructive forces beyond our control... one that shakes us out of our ingrained habit of caring mostly for ourselves and those around us.

The current crisis in Asia is one such calamity. It has inflicted untold damage and casualties that can still only be guessed at, on some of the poorest places in the world.

Two of them - Sri Lanka and Aceh province in Indonesia - have recently suffered the horrors of civil war. At least the tsunami puts those conflicts into some kind of perspective.

But it is in my experience since I became Ambassador for Unicef in 2001, that the more we know about these things the more we realise what we do not know. Even now, only the sketchiest of reports have come in from the remotest and worst-affected communities.

There is an especially worrying lack of information from Nicobar and Andaman islands in the Indian Ocean, directly in the path of the tsunami, where 45,000 people are at risk.

What is tragically clear, however, is that across the affected countries it is the children who have suffered and are suffering, disproportionately. Unicef estimates that one third of the victims of this disaster are children.

The very young are the most vulnerable to the next stage of this killer catastrophe - cholera and other diseases arising from the destruction of fresh water supplies and the contamination of water by whatever human and animal remains may be decomposing in it.

Children need special help and are least able to take care of themselves. Unicef is working first and foremost to keep children in affected areas alive.

Their number one priority is the health, well being and protection of these children who are becoming more and more vulnerable to disease.

Aid flights are giving hope, but are nowhere near enough. With every day that passes the need will grow and I believe that we the British public have a special part to play.

We are a generous people. We are an international people. We need to do our bit.