State immunity — Jurisdictional immunity — Foreign government — Hire of vessel — Commercial purposes — Whether immune from suit — Doctrine of restrictive sovereign immunity — Admiralty jurisdiction — Government-owned ship

Jurisdiction — Admiralty jurisdiction — Convention Relating to the Arrest of Seagoing Ships, 1952 — Effect of “sister ship” jurisdiction — Ship owned by Tongan Government — Arrest of ship in New Zealand — Action in rem — Claim in respect of another ship — Question of possession and control — Jurisdiction under the Admiralty Act 1973 — Plea of sovereign immunity by the Government of Tonga — The law of New Zealand