[zaccus]

Traditionally, middle class has always meant that you own your own business.

A hot dog vendor who owns their own cart is middle class. A doctor who works for a hospital is not. It has nothing to do with income or prestige.

[mattnewport]

We're talking about the UK here, I've never heard that definition in the UK and any definition of middle class that excludes doctors in the UK seems way out of line with how the term is generally used in my experience.