(4)A person who was a British subject immediately before the date of the commencement of this Act and does not become a citizen of the United Kingdom and Colonies by virtue of any of the foregoing provisions of this section shall on that date become such a citizen unless(a)he is then a citizen of any country mentioned in sub-section (3) of section one of this Act under a citizenship law having effect in that country, or a citizen of Eire; or(b)he is then potentially a citizen of any country mentioned in sub-section (3) of section one of this Act.
