The mineral is an essential component of batteries for smartphones and laptops, making billions for multinationals such as Apple and Samsung, yet many of those working to extract it are earning as little as 8p a day in desperately dangerous conditions.

With little regulation requiring companies to trace their cobalt supply lines, and most of the world’s cobalt coming from the Democratic Republic of Congo, the chances are your smartphone contains a battery with cobalt mined by children in the central African nation.

The Sky News team visited a string of mines in the DRC’s former Katanga Province and found children working at all of them.

Eight pence a day for backbreaking work

At one cobalt mine, children toiled in the drenching rain carrying huge sacks of the mineral.

Dorsen, eight, had no shoes and told us he hadn’t made enough money to eat for the past two days – despite working for about 12 hours a day.

His friend Richard, 11, talked about how his whole body ached every day from the tough physical work.

The mine tunnels are dug by hand by miners who have no protective equipment. The tunnels have no supports and are prone to collapse, especially in the rain.

At one mine we travelled to, workers had downed tools in support of a fellow miner who had died after one such collapse.