If you should see something you consider suspicious it is essential that you should report it to the Police immediately - not later, not tomorrow, not to someone else. You are the only one with the details and the only one able to give a full account when you report. Doubts sometimes enter into peoples' minds when they consider reporting an incident to the Police.
Dial 999:
where a crime is in progress
where there is a danger to life or risk of injury
where an offender is still at the scene or has just left it.
Non emergencies
If you see anyone acting suspiciously or
have any information relating to a crime call : 101.
PLEASE NOTE THAT IN AN EMERGENCY, ALWAYS DIAL 999
Crime Reporting Guidance