It's hard for us to imagine life without the humble loo. It's a basic necessity; a UN-recognised human right. However, for an overwhelming two thirds of the population in South Asia, a loo is a luxury that's out of reach.

This week, David Cameron sets off to Liberia's capital, Monrovia, for influential UN talks on what should replace the Millennium Development Goals (MDGs) when they expire in 2015. The cynics would say this is another talking shop, an opportunity for the great and the good to come together and pontificate on poverty. I am not one of them.

The key theme at this year's Stockholm World Water Week is water and food security: how do we meet the ever developing needs of a growing population with an increasing demand for resources?

Cholera is a word that fills the world's poorest people with dread, but if asked, the average person in the west would probably know little apart from what is gleaned from foreign correspondents reporting from hellish refugee camps.

Rwanda, which suffered a brutal genocide in 1994, is the only Sub-Saharan African country on track with its Millennium Development Goal to halve the proportion of people lacking in water and sanitation services by 2015.

But this World Toilet Day (19 November), there are 2.6 billion people across the world who have nowhere safe to go to the toilet. That's two out of five people for whom a toilet is an unimaginable luxury. Meanwhile, almost 900 million people are forced to risk their lives on a daily basis by drinking dirty water because they have no other option.

This confusion about spending and impact may in part be down to the fact that the public don't directly feel the impact of overseas development spending.