Governments perform three functions namely executive, judicial and legislative functions. The role of separation of powers involves the diffusion rather than concentration of powers within the state. Thus, these branches should be separate, unique and equal. The underlying principle of the separation of powers is that individuals have the potential to harm others, and this can become a reality when power is concentrated in one person, faction, or institution. However, if the branches were completely separate it would be unworkable since Parliament is Supreme. There should be sufficient interplay between the branches, for example, the executive proposes legislation, Parliament debates and passes the law, and the judiciary upholds the Acts of Parliament.
The complete separation of powers identified by Montesquieu in the uncodified English constitution no longer exists. The executive in the form of the prime minister and the cabinet is drawn from the largest party in parliament, where strong political parties and non-proportional electoral systems encourage artificially large majorities. The judiciary, too, is not independent of the legislature or executive. The senior judicial officer, the Lord Chancellor, is appointed by the prime minister, sits in the cabinet, and presides over the House of Lords, where the most senior judges, the law lords, also sit. In addition to a separation of powers, Montesquieu identified in England a mixed constitution, a balanced constitution, and checks and balances. William Blackstone, writing at the end of the eighteenth century, analysed and described the mixed constitution more succinctly than Montesquieu. He argued that the English system was different from others. It was not a democracy, aristocracy, or monarchy; it was, rather, a mix of all