Theresa May has refused to rule out using cyber warfare or even taking part in military action against North Korea if it does not stop firing missiles in “illegal” acts of provocation.

Mrs May arrived in Japan on Wednesday morning in the midst of an escalating crisis over Pyongyang’s latest missile launch, and will have lengthy discussions with Prime Minister Shinzo Abe about what can be done.

She arrived with a message for China’s President Xi Jinping, telling him in no uncertain terms that it is his responsibility to rein in Kim Jong-un.