No notice shall be served under section 150 or 161 in respect of a hereditament or agricultural unit, or any part of it, at a time when a notice already served under section 162 is outstanding with respect to it, and no notice shall be served under section 162 at a time when a notice already served under section 150 or 161 is outstanding with respect to the relevant hereditament, unit or part.
For the purposes of subsection (1), a notice shall be treated as outstanding with respect to a hereditament, unit or part—
until it is withdrawn in relation to the hereditament, unit or part; or
in a case where an objection to the notice has been made by a counter-notice under section 151, until either—
the period of two months specified in section 153 elapses without the claimant having required the objection to be referred to the Upper Tribunal under that section; or
the objection, having been so referred, is upheld by the Tribunal with respect to the hereditament, unit or part.