International organization — Officials — Contract of employment — Secondment to another organization — Definition and legal elements of secondment — Whether the two organizations are sole parties to secondment to exclusion of official — Whether terms of secondment can be varied without consent of official concerned — Effect of absence of letter of appointment from receiving organization — Implied fixed-term contract with receiving organization — Termination of fixed-term appointments — Due process — Remedies — Damages in lieu of specific performance — No recovery for remote damage.