“… came to be known as the restrictive theory of immunity, which had by then been adopted by the common law in this country. See Alcom Ltd. v Republic of Colombia[1984] AC 580 at pp. 597-599, Playa Larga and Marble Island (Owners of Cargo Lately Laden on Board) v I Congreso del Partido [1983] 1 AC 244 at pp. 261-262, and Benkharbouch…”