6. Any approval of the Trust required under paragraph 5 must not be unreasonably withheld and—
(a)is deemed to have been given if it is neither given nor refused (with an indication of the grounds for refusal) within 28 days of the submission of the plans for approval or where further particulars are submitted under paragraph 4, within 28 days of the submission of those particulars; and
(b)may be given subject to such reasonable requirements as the Trust may make for the purpose of ensuring the safety or stability of the canal, including requirements as to the construction of protective works.