I've been nice Up until now, I bet things could fucking change.

There has been boss, I've seen it.

The match is now over, but there was also trouble inside the stadium, but still it's having to intervene As rival fans provoked each other.

They were stopped on several occasions after fans invaded the pitch.

The particular type of in group out group psychology I've been researching is called identity fusion, and that's the really extreme type of bonding, where your personal identity is completely fused with your group's identity.

Their behavior serves to protect and defend the group.

When we find for football fans it is as powerful as for people who've been on the front line together, they die for each other.

We think that that relates to the Qin psychology that was so essential to keeping us alive when we lived in tight knit small communities in our ancestral past, we needed communities we could utterly rely on.

So when we get a football match, which is really awful and frightening, actually what you find people come together because it triggers all this ancient psychology that this is a group who is meaningful, who are going to look after me.

And if they feel that another fan is threatened, it feels like a personal attack.

And there have been death.

They're not violent in the name score, but in the name of their love for their fellow fans.