vice versâ

His Britannic Majesty, and His Royal Highness the Prince Regent of Portugal, do stipulate and agree, that there shall be a perfect reciprocity on the subject of the Duties and Imposts to be paid by the Ships and Vessels of the High Contracting Parties, within the several Ports, Harbours, Roads, and Anchoring-places belonging to each of them; to wit, that the Ships and Vessels of the Subjects of His Britannic Majesty shall not pay any higher Duties or Imposts (under whatsoever name they be designated or implied) within the Dominions of His Royal Highness the Prince Regent of Portugal, than the Ships and Vessels belonging to the Subjects of His Royal Highness the Prince Regent of Portugal shall be bound to pay within the Dominions of His Britannic Majesty, and vice versâ.