If you are of interest to a law enforcement agency, and if you use anonymizers or VPNs or encrypted messaging, that is likely to increase their interest and bring closer scrutiny. If they have a decently plausible justification, they may be able to obtain a warrant (or UK equivalent, if different) for access that is much more intrusive than metadata collection, and much more likely to succeed in obtaining information about your activities in connection with whatever caught their attention in the first place.
The short version: if the police are interested in you, they generally will find ways to investigate you.
Biting the hand that feeds IT
