I am advised:
All police positions attached to Police Districts or Police Area Commands are flexible resources. These resources are supplemented by officers from specialist Commands, which are managed centrally, but can be deployed across Police Districts and Police Area Commands to respond to changing crime patterns and emerging issues.
Since 2006, there have been several changes, including the reengineering of Police Districts and Police Area Commands. As a result, it is not possible to make valid comparisons between staff numbers over the period since 2006. In Northern Region, there has been an overall increase of 220 authorised police positions and 61 police officer headcount.