Doesn't really make sense to say that politicians are structurally in power in Westminster though. I mean, yeah, kind of by definition in a democracy the political classes are structurally in power.
Not in the way that we have in the UK - where most representatives (regardless of party) have gone through the same schools and the same social circles (bit of journalism, bit of finance, all largely in London or surrounding areas).
I know so little about British politics that I take Yes, (Prime) Minister at face value. I would have thought it war more about the (benefits and) interests of bureaucracy and civil service.