Amid last-minute campaigning, a string of high-profile speeches and dozens of media interviews in New York, Ban Ki-moon last week took a few hours off to buy dinner for the burly bodyguards, supplied by the State Department, who had been looking after him round the clock.

The South Korean foreign minister “wanted to thank them for working so hard”, says an aide to the man who will almost certainly become the next secretary-general of the United Nations.