Drive down the main roads in Pakistan, and you cannot avoid seeing huge yellow tankers emblazoned with the words ‘Pakistan State Oil’. Mehmood Kot, a small town (population 35,000) in the Punjab, is one of the places where the tankers stop to refill their tanks.

A sticky residue of oil remains in the bottom of the tanks once the tankers have offloaded and before they refill. This can be collected by following behind, catching drips in a container or by climbing inside to scrape oil up. The job attracts youngsters wanting to make a little extra money.