remember flashing your lights ONLY means that you are alerting other road users to your presence. That is the only use the law recognises.

If your stuck behind a mong, one or two flashes will achieve that aim, even if they are half asleep as thier retina is burned out through the rearview mirror.

If you sit there like so many BMW mongs with your finger on the mainbeam constantly flashing them, as your too impatient to wait 5 seconds, then quite frankly you deserve to get convicted.