Permission to be taken for development, etc.

After a notice approving the date of operation of the plan is published under section 11, no person including the Department of Government shall undertake or carry out development of any land or building in the zone unless permission for such development has been obtained in writing from the Authority in accordance with the provisions of this Act : Provided development of any land begun by a Department of Government or any local authority before the commencement of this Act may be completed by that Department or local authority.