I seem to have started to attract some door bell ringing from the local
youths on the skulk home from school. I ignore it - but it has escalated
into them coming up to the windows and knocking on them (to really impress
their mates)

I am thinking of leaving a video camera running in the house - positioned in
such a way that no-one just walking past on the pavement will be caught in
shot. Then if I get a picture of a face at the window I can show it to my
local Community Police Boy.

Any legal issues that you can imagine? Anyone at the window will be 15 feet
onto my property.