Surrounded by latrines and soap dispensers, sanitation charity founder Bindeshwar Pathak is most at home with toilets, which he vows to build in every impoverished home in India.

Affectionately known as India's "toilet guru", 71-year-old Pathak has spent four decades working to improve sanitation in a country where half of the population relieve themselves in the open air.

Inspired by Mahatma Gandhi, a champion of cleanliness, Pathak has more recently been spurred on by new Prime Minister Narendra Modi who wants to make India free of open defecation by 2019.