Who was the last 'working class' British PM?

[J. J.]

Are we talking about a working class background (with the PM upwardly mobile into the middle class in cultural sensibilities and demeanor), or still having a working class style while PM? Was Major really from working class roots, or lower middle class ones, regarding cultural sensibilities?

I think so.

Major was the last really "working class" origin PM.

[J. J.]

Failed garden gnome manufacturer sounds like the most lower middle class profession I've ever heard of (although it could, ironically, also be the most upper class profession imaginable. But that's true of a lot of things, of course).

The guy didn't even complete high school; that is not exactly Establishment.