General Clauses Act, 1897
17. Substitution of functionaries
(1) In any 12[Central Act] or Regulation, made after the commencement of this Act, it shall be sufficient, for the purpose of indicating the application of a law to every person or number of persons for the time being executing the function of an office, to mention the official title of the officer at present executing the functions, or that of the officer by whom the functions are commonly executed.
(2) This section applies also to all 12[Central Acts] made after the third day of January, 1868, and to all Regulations made on or after the fourteenth day of January, 1887.