THE State speaks with one voice in international law. And that voice, of course, is the executive's, usually, but not invariably, that of the Foreign and Commonwealth Office (FCO). Upon a variety of matters a certificate as to certain facts issued by the executive will be regarded by the courts as conclusive of them. This function was, historically, a matter of common law though there are now several statutory provisions in that regard, most notably the Diplomatic Privileges Act 1964 s. 4 and the State Immunity Act 1978 s. 21 identifying defendants who will have immunity from the jurisdiction (see [1998] C.L.J. 4).