"I am increasingly inclined to believe a significant number of drivers are on their phones at stationary points in traffic. E.g. Traffic lights. Where there is quite often a big pause once lights turn green whilst first driver In queue gets off their phone. Not sure what to do about it? From above they do not like it when you tell them to stop. Touching the vehicle is another thing they do not like."
I've started going up alongside them, taking my camera off my helmet and pointing it straight at the phone for a few seconds, then cycling off and reporting it to the police. So long as the footage is clear, the police will generally prosecute (Example:
I also make sure to point out (like in that example) that if they're on the phone as soon as they stopped, they most likely had the phone in their lap while driving.