3. A regular police officer who makes such a transfer election shall, no later than the last day of the period of 3 months mentioned in paragraph 1(a) or (b), as the case may be (or such longer period as the police authority may allow in accordance with paragraph 1), pay all pension contributions then payable by that officer under the 1987 Regulations, including any payment the officer has undertaken to make under regulation F4 or F5 (previous service reckonable on payment) of those Regulations, and all periodical contributions then payable by that officer under the Police Pensions (Purchase of Increased Benefits) Regulations 1987.