“age next birthday at the notional commencement of pension contributions under the 1987 Regulations”, in relation to a regular police officer, means the age that officer would attain on the birthday following the date on which that officer would have attained an exact age determined by subtracting the length of that officer’s qualifying service under the 1987 Regulations from that officer’s exact age on the date when that officer commenced paying contributions under these Regulations, where–

“qualifying service” and “qualifying service under the 1987 Regulations” mean the period in years the officer was entitled to reckon as pensionable service under the 1987 Regulations, except that where some or all of the service the officer was so entitled to reckon was part-time service it means the period in years that officer would have been entitled to reckon as pensionable service if in any period of part-time service that officer had served full-time.