For the purposes of Chapters 1 and 2, an expression in the first column of the following table is defined or otherwise explained by the provision of this Act specified in the second column.
A power under Chapter 1 or 2 to give a direction—
includes a power to vary or revoke the direction by a subsequent direction, and
must be exercised by giving the direction in question in writing.
The amendments made by sections 116 and 117 and Schedule 8 to provisions of subordinate legislation do not affect the power to make further subordinate legislation amending or revoking the amended provisions.