Part III Miscellaneous and Supplementary

21 Evidence by certificate.
A certificate by or on behalf of the Secretary of State shall be conclusive evidence on any question—
(a) whether any country is a State for the purposes of Part I of this Act, whether any territory is a constituent territory of a federal State for those purposes or as to the person or persons to be regarded for those purposes as the head or government of a State;
(b) whether a State is a party to the Brussels Convention mentioned in Part I of this Act;
(c) whether a State is a party to the European Convention on State Immunity, whether it has made a declaration under Article 24 of that Convention or as to the territories in respect of which the United Kingdom or any other State is a party;
(d) whether, and if so when, a document has been served or received as mentioned in section 12(1) or (5) above.