There will be no further action taken against him for drunk in a public place, the four hours of lock up that he received when caught is viewed as punishment, often for this single offense police tell you not to bother turning up to court because nothing will happen that you need to worry about. The issue is offensive behavior.
Back in uni one of my mates got caught by police doing the exact same thing except he urinated into the gutter outside a police station rather than on it. 4 hours in the slammer to sober up...court the next month with a diversion notice issued, so basically just a warning.
However much media attention atm is on zero tolerance of drunk youths so Johnson may cop it a little harder as he is a role model.
