1U.K.If a diplomatic agent passes through or is in the territory of a third State, which has granted him a passport visa if such visa was necessary, while proceeding to take up or to return to his post, or when returning to his own country, the third State shall accord him inviolability and such other immunities as may be required to ensure his transit or return. The same shall apply in the case of any members of his family enjoying privileges or immunities who are accompanying the diplomatic agent, or travelling separately to join him or to return to their country.