Jeremy Vine once wrote a story about Boris Johnson which I thought was the pinnacle of this. It was published on his Facebook page and I've since lost the link, so you're going to have to read it on Reddit where someone has posted the whole thing again.

It is uproariously funny and very relevant.

https://www.reddit.com/r/ukpolitics/comments/c1korj/jeremy_v...

It tells the tale of how the man who was going to become Prime Minister of the United Kingdom used to play the improviser and ex tempore comedian, in a practiced and automatic way.

Here's the original: https://news.ycombinator.com/item?id=20281420