Saroo Brierley got himself lost when he was five years old. After living off the streets of Calcutta fending for himself, he was eventually adopted by an Australian family. Years later, with only his childhood memories to guide him, Saroo figured out where he was from using Google Maps and tracked down his mother he hadn't seen in 25 years.

Saroo settled down well in his new home. But as he got older the desire to find his birth family became increasingly strong. The problem was that as an illiterate five-year-old he had not known the name of the town he had come from. All he had to go on were his vivid memories. So he began using Google Earth to search for where he might have been born.

"It was just like being Superman. You are able to go over and take a photo mentally and ask, 'Does this match?' And when you say, 'No', you keep on going and going and going."

Eventually Saroo hit on a more effective strategy. "I multiplied the time I was on the train, about 14 hours, with the speed of Indian trains and I came up with a rough distance, about 1,200km."

He drew a circle on a map with its centre in Calcutta, with its radius about the distance he thought he had travelled. Incredibly, he soon discovered what he was looking for: Khandwa. "When I found it, I zoomed down and bang, it just came up. I navigated it all the way from the waterfall where I used to play."