It appears that the reason Boris Johnson has been installed as Foreign Secretary was due to a misunderstanding.
Apparently an "aide" sent Theresa May a list of people who would support her,if given a position.
Boris Johnson's name was on the list - Theresa May wrote "F/Off" beside his name and the "aide" thought it meant Foreign Office and released it to the press before the mistake was noticed.
Sounds believable to me !
