The highway leading out of Delhi is lined with adverts for new housing developments with names such as “Exotica Dreamville”. A typical hoarding shows a smiling young couple, standing on a manicured lawn, under the slogan: “Lifestyle is here.”

Keep driving, however, deep into the neighbouring state of Uttar Pradesh, and you will find lifestyles that are neither exotic nor the stuff of dreams. On the outskirts of the city of Budaun, many of the children show signs of malnourishment. Goats, buffalo, cows and camels roam the filthy streets. Unicef, the UN agency for children, is running a campaign to equip all the houses in the district with a modern toilet. It is also trying to find new work for the “manual scavengers”, who make their living by cleaning dry latrines by hand.

In Budaun itself, the sanitation project is making slow but steady progress. But for Uttar Pradesh – whose population is more than 200m, larger than that of Brazil – the task is still dauntingly big. Unicef estimates that only 21 per cent of the state’s inhabitants have access to a proper toilet. In India as a whole about 600m people – out of a total population of 1.2bn – still practice “open defecation”, either in fields or urban wasteland.