The man who makes money where no one else dares to go

The mineshaft is dark, the air humid and starved of oxygen. I follow Marcus Edwards-Jones out of the muddy tunnel towards a window of light and at last we emerge into the evening. The sun is going down over Rwanda’s green hills, dotted with banana groves and eucalyptus stands, with a river snaking away into the distance. Around us are men carting away lumps of rock, which on close inspection are streaked with veins of a black metal called tantalum, a high-value mineral used in the manufacture of mobile phones, nuclear reactors and spaceships.

‘I’ve never seen a deposit like this,’ says Marcus. ‘It’s all been worth it.’ I first met  Marcus in Oxford in 1985. We said hello on the stairs at a Piers Gaveston party, both of us dressed in togas. Soon after that I returned to Africa to be a correspondent, while he went into the City to work in brokerage firms.