66.—(1) An election to pay a lump sum—
(a)must be made by notice in writing given to the Board not later than 12 months after the date on which the person last became employed by the Board as a firefighter; and
(b)if the sum is not paid within three months after the date on which notice was given, shall be treated as not having been made.
(2) An election to pay periodical contributions must be made by notice in writing given to the Board at least two years before the person’s normal retirement age, but no such election may be made where he and the Board have agreed that he will leave the scheme with an entitlement under any of articles 11, 12, 13, 15 and 16.
(3) Unless paragraph (1)(b) applies, an election under this article—
(a)takes effect on the day on which the written notice is received by the Board; and
(b)is irrevocable once the lump sum has been paid or, as the case may be, the first contribution has been deducted.