To North Koreans, their country’s relationship with China was “forged in blood in the victorious war to liberate the fatherland” — a conflict that most of the world calls the Korean war. In China, ties with the Democratic People’s Republic of Korea have traditionally been described as being “as close as lips and teeth”.

These days, however, teeth are bared and lips curled on both sides. The Financial Times visited North Korea last week. Most striking was the deep animosity that everyone, from government officials to ordinary citizens, seemed to feel towards their former comrades across the border.

All interviews were conducted in the presence of minders and no one was free to say what they really think. That only made the anger at China more striking, since it means such attitudes carry a certain amount of official approval. Although the ruling North Korean Workers’ Party held its first congress in 36 years last week and the country is China’s only official ally, no senior official from Beijing attended.