Separation of Powers

The Courts and Tribunals Judiciary's own guidance on the justice system explains that 'the justice system is one of the three branches of the state', alongside 'the executive, or the government, and the legislature'. It notes that 'in most democracies these three branches of the state are separate from each other', with roles defined so as to prevent 'the concentration of power in any one branch and enabling each branch to serve as a check on the other two branches' — 'this is known as separation of powers'. The judiciary's guidance is candid that the UK has never observed this doctrine strictly: historically 'the British constitution did not separate and indeed mixed the three branches of the state', most visibly in the old office of Lord Chancellor, who was simultaneously a Cabinet minister (executive), a judge and head of the judiciary, and the Speaker of the House of Lords (legislature).

That overlap was substantially reduced by the Constitutional Reform Act 2005, which followed the government's 2003 proposal to abolish the office of Lord Chancellor. The judiciary's guidance records that the Act 'brought about a significant change in the nature of the office, essentially removing the Lord Chancellor's position as a judge and head of the judiciary of England and Wales, and position as the Speaker of the House of Lords'. The Act itself, in section 1, states that it 'does not adversely affect' 'the existing constitutional principle of the rule of law', and it created the separate UK Supreme Court, transferred the Lord Chancellor's judicial functions to the Lord Chief Justice, and established the independent Judicial Appointments Commission — all reforms aimed at reinforcing the separation between the judicial branch and the executive and legislative branches.