The need for statutory powers was explained in Chapter 2. One of the reasons for obtaining statutory powers is to legalise compulsory purchase: a landowner need not sell his land against his will unless compelled to do so by the law, though in practice the knowledge of the existence of compulsory purchase powers in the background is sufficient to persuade most owners to sell to an acquiring authority without the need for the ultimate sanctions of the law to be applied. This chapter outlines the various sources of compulsory purchase powers; apart from royal prerogative, they are all statutory in origin.