There has to be pre-meditation otherwise it is merely a random act of violence. I don't think that somebody is overcome with spontaneous support of a type of cause that woulld include terrorist acts in its strategy at the precise time of commiting an act of violence.
I do not believe there is a definition of terrorism that cites pre-meditation a fundamental requirement. Terrorism is violence with an underlying
political motive. Political being the key attribute rather than how far in advance it had been planned. Whilst yes, generally all significant acts of terrorism
are planned well in advance in order to cause most devestation, that isnt the defining point.
For example somebody might pre-meditate a murder. But if that murder was drugs related and they were just popping off the boss of a rival gang then its not terrorism. Because there is no political motive.
So really in the case of Farage vs the milkshake the aspect of premeditation isnt the one that really needs to be considered, as to if it was terrorism or not. Whether or not the milkshake throwing is considered
violence is aspect you should be considering. In hindsight possibly not, but then again I suppose that depends what the cup was made of and was it thrown as his head. Then I have to ask if im really that bothered what it is, I just called it terrorism as I knew it would ruffle a few feathers.