In case of any Vacancy in the Office of Commissioner of Police of the Metropolis, or in case of the Illness or Absence of any such Commissioner, it shall be lawful for such One of the said Assistant Commissioners as may be authorized by Writing under the Hand and Seal of One of Her Majesty's Principal Secretaries of State for this Purpose to do all such Acts as it would be competent for the Commissioner of Police of the Metropolis to do, and all Acts done by any Assistant Commissioner so authorized shall be as valid and effectual as if done by the Commissioner of Police of the Metropolis if the Office had not been vacant, or (as the Case may be) if the Commissioner had been present and acting.