Diplomatic and consular intercourse and privileges — Permanent diplomatic envoys — Privileges and immunities of diplomatic envoys and their staff — Vienna Convention on Diplomatic Relations 1961, Articles 31 and 39 — Plea of immunity from suit before courts of receiving State — Appointment of and termination of functions of attaché — Vienna Convention, Articles 9, 10 and 43 — Non-recognition by receiving State of attaché of sending State — Persona non grata — Whether functions of attaché terminated — The law of the Federal Republic of Germany