v"Then there is the desire for fans to assert themselves over their rivals.
"The fan groups will bring to the fore those background factors and so start a mutual spiral of provocation and intimidation."
But Prof King says this does not always lead to violence, numbers are key too.
"What you need is a critical mass on both sides - and what seemed to happen in this case was that all three elements were aligned."
Prof King says the result of the game is not necessarily the trigger for violence.
"Hooliganism is not caused by what goes on on the pitch, although it can be a factor in the intimidation and can precipitate violence.
"If there's a late goal, like there was last night, a sense of disappointment and grievance is heightened, and conversely a sense of euphoria on the other side.
"A bad foul on a player can have the same effect.
"All you need is a small group of motivated people - the men involved can't be seen to be backing down from their mutually avowed rivalry."
So what does Prof King think can be done ahead of the 11 December fixture, which will see the teams face each other at Home Park once again?
'Pre-emptive bans'
"British police are actually quite good at this sort of thing now - especially compared with other places in Europe.
"An immediate thing is obviously to increase levels of policing.
"Pre-emptive bans have been proven to work, how we feel about that as a society is another matter.
"The way ticketing is organised can be really important, but again that can be unpopular."
So is there any way of stamping out violence altogether?
"In the longer term I'm really sceptical that hooliganism will ever disappear," said Prof King.
"I think violence will always be part of football, it's just about mitigating it when and if you can."