Agree lillam.

Presumably this is related to the serial granny rape cases - the incidents radiate from Forest Hill it seems.
To make suggestions on how the police run their investigation would suggest they do not know what they are doing.
But rather than interviewing everyone in FH, surely it would be better to target certain groups - like those who work in old peoples homes, and hospitals, anyone who has regular contact with older people.
This may sound unfair, but you have to focus and be logical and start somewhere. Old people are as vulnerable as children so I'd prefer police checks run on all staff dealing with them in any case. This would establish their address as a minimum.