17The authority of the Corporation in respect of a design may be given under paragraph 13 or 14 either before or after the design is registered and either before or after the acts in respect of which the authority is given are done, but not so as to authorise the doing before the appointed day of any act; and such authority may be given to any person whether or not he is authorised, directly or indirectly, by the registered proprietor to use the design.