(5) For the purposes of the calculation in Article 18(3), where:
(a)in any income tax year commencing after 5 April 1975, an employed person has completed periods of insurance exclusively in Ireland and the application of paragraph (3) results in that year being a qualifying year under the legislation of Great Britain, Northern Ireland or the Isle of Man, he shall be deemed to have been insured for fifty-two weeks in that year;
(b)any income tax year commencing on or after 5 April 1975 does not count as a qualifying year under the legislation of Great Britain, Northern Ireland or the Isle of Man, any periods of insurance completed in that year shall be disregarded.