1Where a compulsory purchase order authorising an acquiring authority to acquire any land has come into operation, the authority may execute in respect of any of the land which they are authorised to acquire by the compulsory purchase order a declaration in the prescribed form (in this Schedule referred to as " a general vesting declaration ") vesting the land in themselves as from the end of such period as may be specified in the declaration (not being less than twenty-eight days) from the date on which the service of notices required by paragraph 4 below is completed.