I note, in your response to PA of Leeds that you again make the point that headlights should only be flashed as a warning. In this regard, a couple of days ago, I passed a collection of policemen and assorted police vehicles stopping oncoming traffic. They appeared to be selecting particular vehicles. A little further along the road I passed a stationary police van with open flaps at its rear with cameras pointing out. This was obviously the van that was alerting the roadblock down the road to speeding vehicles or whatever. Having passed this van, and in a spirit of solidarity with my fellow motorist, I flashed my headlights at oncoming traffic to warn them of the "danger" ahead of them. Was I doing the right thing?