or some twat in his BMW/Merc/smart looking convertible thinking he is the dog's bollocks with his bird/girl mates in the car and he tries and makes himself look the big man by thinking he can take you on and impress his bird/mates...

Guy in his convertible BMW 318Ci tried that with me. I launched it and got about a car length in front and managed to hold it. His face was a picture at the roundabout where we slowed down!