Where an eligible pensioner was granted an increase in the annual amount of his pension in pursuance of section 11 of the Superannuation Act 1957 , section 4 of the Superannuation (Pension Increases) Act 1961 , section 26 of the Superannuation Act 1963 or section 4 of the Superannuation (Pension Increases) Act 1967 , any increase in the annual amount of his pension to which he is entitled under the preceding provisions of this Act shall be reduced by the amount of the first - mentioned increase.