Immediately before the commencement of the poll, the presiding officer must show the ballot box empty to such persons, if any, as are present in the polling station, so that they may see that it is empty, and must then lock it up, if it has a lock and (in any case) place the officer’s seal on it in such a manner as to prevent the box being opened without breaking the seal and must place the box in the officer’s view for the receipt of ballot papers, and keep it so locked and sealed or sealed (as the case may be).