Days into an official government tour, the North Korean minder finally loses patience with his foreign 'guests'. "I can't stand it. I can't stand it", he shouts at author Bradley Martin. He cannot comprehend how Martin could claim Pyongyang started the Korean war. "If you say that again, I can't secure your life in this land!" Angrily, the guide, Mr Kim, goes on to denounce American aggression in Korea. At the demilitarized zone separating North and South Korea, there's a real sense the nation feels under attack. "Freezing the Yongbyon nuclear power station does not mean we'll give up nuclear weapons", states Captain Han. "We will counter violence with violence". For Mr Kim, life has improved considerably in the past decade. "We now have two or three hours of water and electricity every day". But even he admits that during the great famine; "there were many difficulties for my family". There are signs North Korea is trying to develop its economy by opening up to foreign business. But with nuclear tensions so high, how many companies are prepared to invest?