Which British prime minister did Niels Bohr meet to discuss international cooperation on atomic weapons?

Niels Bohr met with British Prime Minister Winston Churchill to discuss the necessity of international cooperation regarding nuclear weapons and the importance of sharing information with the Soviet Union to prevent a postwar arms race.1

Bohr, a renowned Danish physicist, believed that the urgency of the atomic project required a new approach to international relations. However, his efforts were unsuccessful; Churchill remained unconvinced and even grew suspicious that Bohr might be spying for the Russians.1