SASless, I have no information on the mission being flown during/prior to the accident, only second hand speculation on here.
Routine helicopter patrols are (or certainly were in my time, well before NPAS days) deemed too expensive and a waste of aircraft hours, which could not be justified to the taxpayer. The ASU responded to actual task requests, as required by the control rooms (we were a joint force unit).
The (police) members of the crew at my unit did have the authority to "self launch" to a developing situation if seen appropriate; for that reason the radios of both forces were constantly being monitored by the unit. The only "patrolling" done was the return flight from a completed task.