(1) Invalidity pension is not payable to an invalid if:
(a) CSC is satisfied that the physical or mental condition that is the basis of the invalid's medical discharge was caused, or substantially contributed to, by an event that happened while he or she was absent without leave and more than 21 days after that absence started; and
(b) his or her salary for the period of absence before the event was forfeited under regulations made under the Defence Act 1903 ; and
(c) an amount equal to that forfeited salary is not later paid or payable to him or her under those regulations.
(2) Subsection (1) does not apply if the CSC is satisfied that the circumstances of the absence are such that the subsection should not apply.