The amount of an injury pension, calculated as aforesaid, shall be reduced, where the person concerned received the relevant injury (within the meaning of Regulation B4) during a period of service as a regular policeman, by three-quarters of any other pension calculated by reference to pensionable service reckonable by reason of that period of service.

For the purposes of sub-paragraph (1), such other pension as is there mentioned which is reduced in accordance with the provisions of Regulation B7 or B9 (commutation and allocation) or of Part VIII of this Schedule (reduction related to up-rating of widow’s pension) shall be deemed not to have been so reduced.