A parliament elected by first-past-the-post. This ensures that conservative governments can run most of the time on a minority of the vote, and in practice transfers real democratic agency from the people at large to a small number of conservative leaning districts called 'marginal constituencies'. Without this, the country would have been historically more left-wing in law making, and would probably be more like many Continental countries, with better workers rights and less precarity, improved housing for ordinary people, better regulated financial system, stronger and sophisticated local government that involved more people, etc.