Many people observe that political power in Canada has become increasingly concentrated in the hands of the Prime Minister over course of the last few governments.

Some compare it to the days of MacKenzie King and Louis St. Laurent, when cabinet ministers had greater autonomy.

Has this trend been in evidence since Confederation? Or since parties have used the personalities of the leaders to push for popularity (i.e. starting with Diefenbaker.)

What about the courts? Or the Senate? Where do they fit in?

I'm mostly interested in Canadian politics, but insights about other Westminster-style parliaments might be helpful.