I think spot has pretty much nailed it re Johnson. I think May is pretty aware of it too, which is why she's put him in as one of the brexit leaders. Now he has to personally face the consequences of his lies on our foreign relations and make something he knows is a disaster into a success, or know that he will be lambasted by historians for centuries to come.
It would not surprise me at all to find he scored quite highly for psychopathy.
(Johnson, not spot. Just to be clear

)