For the purpose of calculating the retirement grant of a Class B member, his pensionable remuneration shall not exceed £100,000 (or such other sum as may for the time being be specified by the Treasury for the purposes of section 590(3) of the Income and Corporation Taxes Act 1988 as that section continues to have effect as respects Class B members by virtue of paragraph 18(2) of Schedule 6 to the Finance Act 198995).