You've made the point better than I. I did take Political History for O level, so remember some of the rules, but guess it comes from experiencing the changes for myself.
Who a decade later stepped down for Eden, who stepped down for MacMillan, followed by Douglas-Home.
I think the constitution should be taught in schools as part of history.
I am surprised at how many times I've read this since yesterday. It's not as if a Prime Minister hasn't ever changed before without a General Election. Brown took over from Blair, Major took over from Thatcher, Callaghan took over from Wilson.