15A pension payable by a Secretary of State under the [1948 c. 24.] Police Pensions Act 1948 to a person who at the time of his retirement—
(a)was engaged as mentioned in section 1(1) of the Police (Overseas Service) Act 1945 ; or
(b)was engaged in service in respect of which the provisions of section 5 of the [1958 c. 14.] Overseas Service Act 1958 had effect; or
(c)was serving as an inspector or assistant inspector of constabulary under the [1964 c. 48.] Police Act 1964 or the [1967 c. 77.] Police (Scotland) Act 1967; or
(d)was engaged in central service pursuant to section 43 of the Police Act 1964 or section 38 of the Police (Scotland) Act 1967.
This paragraph includes a substituted pension not so payable if the original pension is so payable.