(1)Where any special agreement or arrangement between the Government of any State and the Government of the United Kingdom in force at the commencement of this Act provides for extending(a)such immunity from jurisdiction and from arrest or detention, and such inviolability of residence, as are conferred by this Act on a diplomatic agent; or(b)such exemption from customs duties, taxes and related charges as is conferred by this Act in respect of articles for the personal use of a diplomatic agent;to any class of person, or to articles for the personal use of any class of person, connected with the mission of that State, that immunity and inviolability or exemption shall so extend, so long as that agreement or arrangement continues in force.
