Sovereign immunity — Foreign States, State-owned corporations and their property — Central Bank of Nigeria — Claim under documentary credit — Whether entitled to jurisdictional immunity — Whether immunity available to organisations legally independent of foreign State — Acts iure gestionis and iure imperii — Whether act to be classified according to nature or purpose — Whether classification to be made according to municipal or international law — Whether application of restrictive theory of sovereign immunity requires special connection between facts of the case and the forum — Whether public interest relevant — Attachment of bank deposits — Immunity from attachment — Whether funds allocated to State public service immune from attachment — Whether possible future use of assets for State activities relevant — The law of the Federal Republic of Germany