5. Where a former professional fireman not subject to the Act of 1925, not later than one month after the appointed day, enters upon employment in the civil service of the Crown, all his approved service under the relevant pension provisions shall, if within three months after he enters upon such said employment he so elects by notice in writing served upon the department of the civil service in which he is employed, be treated, for the purposes of the Superannuation Acts, 1834 to 1946, as if it had been continuous service in an established capacity in the civil service of the State, within the meaning of the said Acts, ending immediately before the date on which he enters upon the said employment, and, in the case of any such former professional fireman as aforesaid other than a person in whose case the National Fire Service (Preservation of Pensions) (General Pension Funds) Regulations, 1941(1), had effect immediately before he ceased to be employed in the National Fire Service, shall be so treated in the following proportion, that is to say, three years of such approved service shall be treated as equivalent to four years of such service in the civil service of the State, and any other period of such approved service shall be treated in the same proportion.
I, p. 325.