> This is very different from the UK system, where each party and its leader agrees on their platform for the next election, publishes it as a manifesto, and runs collectively on the promise of enacting those policies if they win.

Not what Tory MPs say. They say things like

  > Neither Cabinet, MPs nor Party Policy Forum ever saw or debated it. It was roundly rejected 
  > and widely agreed to have cost us our majority, leaving the mandate in Parliament, not the 
  > Party. (As I wrote in @Telegraph the morning after). Lost majority=Lost mandate.