I remember a similar situation flying out of LHR as SLF on an Arab carrier a few years back. A young Arab guy in transit from the U.S. was obviously high on uppers and running around the cabin during taxying.
I was concerned that CC were remaining in their seats and doing nothing however then a large gentleman who I later understood to be a Sky Marshall, appeared from the front of the aircraft, grabbed the young man, dragged him into the rear galley and , judging by the screams and other sounds of violence, gave him a jolly good thumping! While this wasn't pleasant to witness, it certainly worked and there was no further trouble from the perpetrator.