21. A person may not commute under article 18 or allocate under article 20—
(a)so much of any pension that it becomes payable at a rate less than two thirds of the rate at which it would have been payable but for those articles and Parts VI and VII of Schedule 2; or
(b)in the case of a deferred pension in relation to which, when it becomes payable, he has a guaranteed minimum, so much of the pension that its weekly amount, including any increase under the Pensions (Increase) Act (Northern Ireland) 1971, is then less than the guaranteed minimum.
(c)For the purposes of this article no account shall be taken of any increase under article 69(3) or rule 2 or 3 of Part 7 of the Compensation Scheme in an award to a serviceman.