(1) Subject to subsections (2) and (2A), notwithstanding anything in the rules of a scheme, where a benefit provided for under the rules is payable in the form of an annual pension and such benefit has commenced, the trustees of the scheme shall not reduce the amount of the benefit payable to such person in any subsequent year below the amount of benefit payable in the preceding year.

(2) The trustees of a scheme may reduce the amount of a benefit to which a person is in receipt under the scheme -

(a)

(i) where the benefit has been determined without taking into account a pension payable to the person and where the rules of the scheme permit the subsequent reduction of the benefit by taking into account such pension at or after the date at which that pension commences to be payable to the person, or