State immunity — Jurisdictional immunity — Commercial activity exception — Distinction between commercial acts and sovereign acts — Distinction turning on nature rather than purpose of act — Whether recruitment of staff for a hospital a commercial activity — Recruitment of staff in United States to work in hospital in Saudi Arabia — Alleged false imprisonment and ill-treatment of member of staff by agents or employees of Saudi Government — Whether sufficiently closely connected with employment contract — Whether sufficient connection with the United States — United States Foreign Sovereign Immunities Act 1976 — The law of the United States