I know a couple of people who worked for / with him when he was the Mayor. They said he was always the smartest guy in the room. As sharp as a tack. Also very charismatic (apparently it was the same when he was at Eaton). However he was bone idle. Great at painting the big picture, but useless on detail and didn’t know the meaning of hard work. That was something for his minions to do for him. He also cultivated his disheveled, bumbling, comical persona to disarm people. He believes he was born to rule and played his cards perfectly with Brexit to get to the top of the Tory party. A large part of the general public fell for it and he only had Corbyn to beat. The right place at the right time…
I have never bought in to the view he is super intelligent.
With some people, the occasional references to Latin, Roman history and Byzantine art are impressive (not necessarily those you know). He is simply regurgitating what he studied at Oxford (Classics). I could quite easily reference Aristophanes, Heraclitus, Socrates, Kant, Schopenhauer, Jean Jacques Rousseau, Modigliani, Hayek et al. That doesn't make me intelligent. It simply means I studied PPE and I am a pompous tosser.
Now I have no idea if he is especially intelligent or not but there are anecdotes from people who suggest he is not bright. He seemingly lacks emotional intelligence.
There are many people in this country who seem to show deference, no doubt as they are impressed, to those who use the occasional 'a prori', 'acta non verba', 'ergo' and 'mea culpa' when they speak. Many Tory MPs (e.g. Jacob Rees-Mogg), highbrow paper columnists and presenters of arts programmes have done this for several years. I find it incredibly irritating. It's not as if these words or phrases do not have a simple English equivalent. I believe the relevant term here is grandiloquence.
Bloody hell, that was a rant!