The CMA may, within the period of four weeks beginning with the day on which they are given notice under section 15(4A) above, give a direction to the Office of Rail and Road . . . —
The Secretary of State may, if an application is made to him by the CMA within that period of four weeks, extend the period within which a direction may be given under this section to one of six weeks beginning with the day on which the CMA are given notice under section 15(4A) above.
The CMA may give a direction under this section only if the modifications to which it relates do not appear to them requisite for the purpose of remedying or preventing the adverse effects specified in their report on the reference under section 13 above.
If the CMA give a direction under this section, they shall give notice—
A notice under subsection (4) above shall be given—