The visit was confidential, the subject strategic. The US diplomat Amos Hochstein is used to these trips not appearing on any official agenda. In March, Secretary of State Antony Blinken's main adviser on energy security issues discreetly arrived in Lubumbashi. The mining city, which looks like a quaint rural town, is one of the places where cobalt, copper and a part of the world's energy future are traded. Hochstein, who is said to be close to President Joe Biden, is one of the people devising the