Subject to paragraph 2 and Parts VII and VIII of this Schedule (reductions at state pensionable age and related to up-rating of widow’s pension), the pension shall be of an amount equal to 30 sixtieths of the policeman’s average pensionable pay with the addition, subject to a maximum of 40 sixtieths, of an amount equal to 2 sixtieths of that pay multiplied by the period in years by which his pensionable service exceeds 25 years.