(4ZC) Where subsection (4ZB) does not apply, subsection (4ZD) applies if—

(a) the rules require and, since the relevant time, have always
35required the annual rate of the pension to be increased at
intervals of not more than twelve months, and

(b) there is a part of the annual rate of the pension which the rules
require and, since the relevant time, have always required to be
increased for the purposes of each periodic increase by at
40least—