The train was heading to North West London , there is a lot of both big time and small time gang activity there . Small time gang violence , stabbings and shootings are quite common , for as little as entering another gangs territory .
The guy who remonstrated with him was Black and he didnt seem to fear the drunk guy at all , when the drunk guy stated that he could knock him out with one punch, his reply was "Oh really" in the *we will see* sense .
Even when the drunk guy pulled something out his pocket , which could have been a weapon , the Black guy seemed unconcerned .
I reckon that the Black guy was armed and the drunk guy could quite easily have found himself getting stabbed or even shot