on a dual carriageway yesterday - I was doing 70(ish), traffic in the outside lane, I moved over to the inside lane, so did the car in front to overtake the slower car (no problem there) - I gradually caught him up, but left a decent space between him and me. When he then pulled into the outside lane again, I carried on and overtook him - as I went past, he gave me the finger and several other derogatory gestures.
Can someone tell me what I did wrong.................'cos I haven't got a clue