Hostile states do not usually send their best oboists across the border to infiltrate the enemy. Yet this has been the allotted role of the New York Philharmonic, which played last night in Pyongyang.

While cultural exchanges have already occurred at a low level between western countries and North Korea, the size of this visit, and the fact it is from the US – the main ally of South Korea, with whom the North is still technically at war – is of immense significance.