I'm driving down the A3 tonight on cruise at 70MPH. The road is pretty quiet. Any cars that I catch up, I indicate in plenty of time and pull out to overtake. I must have had at least half a dozen people speed up as I got level with them. I had one guy speed up so I dropped in behind him, he slowed down again. Boot hard down, out round him and back to 70. Why do they do it?