21. (1) If the applicant for registration of a change of name asks the Registrar-General in writing to arrange for noting the change of name in the particulars of the person's birth, and the person's birth is registered in the Register or under a corresponding law, the Registrar-General shall—
(a) if the birth is registered in the Register—alter the Register by changing the person's name in the entry relating to the birth and including in the Register the particulars prescribed for the purposes of this paragraph; or
(b) if the birth is registered under a corresponding law—notify the relevant registering authority of the change of name.
(2) Where a change of name is noted in the Register under subsection (1), any birth certificate issued by the Registrar-General for the person shall show the person's name as changed.