What are the separated powers?
The overlap of powers allows Parliament to make any change it wishes by Act of Parliament and helps to insure against arbitrary exercise of power. There is almost complete separation of powers in the USA where governmental intransigence in controversial matters is a much bigger problem than it is here (here the judges can indulge in greater law making activities if necessary). There is little executive-legislature separation in the UK but much legislative-executive/judiciary separation. The concept of the separation of powers was first discussed by Charles Montesquieu (after observing the British system).
