The separation of powers

One of the fundamental principles underlying the British constitution is that of the separation of powers. According to this principle, developed by the eighteenth-century French philosopher Montesquieu, all state power can be divided into three types: executive, legislative and judicial. The executive represents what we would call the Government and its servants, such as the police and civil servants; the legislative power is Parlia­ment; and judicial authority is exercised by the judges.

The basis of Montesquieu's theory was that these three types of power should not be concentrated in the hands of one person or group, since this would give them absolute control, with no one to check that the power was exercised for the good of the country. Instead, Montesquieu argued, each type of power should be exercised by a different body, so that they can each keep an eye on the activities of the other and make sure that they do not behave unacceptably.

Montesquieu believed that England, at the time when he was writing, was an excellent example of this principle being applied in practice. Whether that was true even then is debatable, and there are certainly areas of weakness now.