Ultimately power extends out the barrel of a gun. Well, sort of.
In the UK, we live in a society that has a strong legal system that to a great extend protects every member of our society. People are not able to take away your home without due legal process even if you don't pay your mortgage. I could steal your car but you'd probably call the police. The police force would detain me and the courts could order me to be imprisoned. If I try to escape the prison guards will use force to detain me.
We often forget how privileged we are in a democracy. Despotic dictatorships often steal property and land from their citizens because they hold all the guns. In a society that has a respect for the law itself, all the people who hold the guns do what the courts and the properly appointed government tell them to do. But a Coup d'etat is simply what happens when the ones with the guns stop following those orders.
So Power extends from the barrel of a gun.
Except for one thing. It really, really doesn't. If you want to talk about real power, power to change people's hearts and minds and not simply force them to act our of fear, well then you need to talk to Gandhi or King or Romero.