The Robbery at the Museum of Great Britain was an attempt by the combined forces of Erik Killmonger and Ulysses Klaue to steal a Wakandan warhammer from the Museum of Great Britain.
In 1992, South African arms dealer Ulysses Klaue was enlisted by Prince N'Jobu of Wakanda to infiltrate the isolationist country and steal a cache of Vibranium. While Klaue's mission was successful, N'Jobu was executed by his older brother, King T'Chaka, after his role in the attack was exposed.
Klaue, meanwhile, was branded with the Wakandan symbol for "thief" as punishment for stealing the vibranium.
Twenty-three years later, Klaue was forced to surrender the metal to the rogue artificial intelligence Ultron, who cut off the dealer's left arm in a fit of rage. Klaue then managed to escape with his life while Ultron and the Avengers engaged in an open confrontation.
Using stolen Wakandan mining technology to create a weaponized prosthetic arm, Klaue proceeded to team up with former black-ops mercenary Erik Stevens before setting out to steal and sell weapons made of vibranium on the black market.