Does North Korea’s Kim Jong-un have a nuclear surprise for President Biden?

• Kim’s nuclear sabre-rattling comes at a fine time, just as the new US leader’s in-tray fills with the messes Trump left in Iran, China and America itself
• But with Pyongyang waving a ‘get out of jail card’ from Beijing, Biden may find this is one area where a Trump-era policy – the Singapore spirit – pays off