Mr John Bolton is reported to have kept a defused hand grenade on his desk at the State Department during the administration of former Republican President George W. Bush, when he served as undersecretary of state for arms control - a role in which he championed the 2003 invasion of Iraq.

Blunt-speaking American diplomats are not unusual, but even by the usual standards, President Donald Trump's 69-year-old incoming National Security Adviser is in a class of his own.