It is arguable that the fundamental change which took place between the ancient world and the modern world was the transition from the rule of a dictator to the rule of law.
In the ancient world - as today - people gave the dictator various titles. They might be called, for example, King, Emperor, Chief or Warlord. The title was unimportant; how they obtained the title was unimportant; what mattered is that their word was law.
In the modern world, the UK has a constitutional monarchy: while the Sovereign is the Head of State, the ability to make decisions about the law resides with an elected Parliament, although the changes do not actually become law until they receive the 'Royal Assent'. In theory, the monarch can choose not to give their assent; in practice, this has not happened since 1708.
So the monarch still sets the law in the UK. But this is a detail: the most important change is not the shift from the monarch to the parliament in deciding what the law should be, but in the recognition that the monarch is subject to the law.
There are disturbing changes to the way the UK is policed in recent years, as can be seen in the Police and Crime Act. See this article from the Bristol Cable about some key steps which led to this legislation: 5 key moments in history that led to the Police and Crime Act.
People argue about the aim of prison - what we are seeking to achieve when we send people to prison. But, whatever the aim, unless we consider the aim to be only detention and punishment, then in the UK it is clearly failing. People come out of prison more likely to commit crime than when they went in, so it neither deters nor reforms.
(See also Prison)