He strongly suspects now that it was a bottle. He woke up in the ambulance on the way to hospital and was told he had been unconscious for five to 10 minutes.

Tony has spoken to police and his name has been withheld to protect his identity.

He is clear on one thing: alcohol was part of the problem.

''I think it wouldn't have happened if everybody was sober,'' he said.

''It was unprovoked. The actual target was another individual who was drunk. In a few seconds it escalated to a head butt and punch.''

Tony tried to play the role of peacemaker and ended up wearing the brunt of an aggressive group's combined anger. He was hit on the back and side of his head and also suffered a blow to the forehead when he fell down, unconscious.

He suffered cuts and bruises and has a permanent scar.

The Australian Bureau of Statistics has found that most victims of physical and face-to-face threatened assault in 2010-11 felt that alcohol or drugs were a contributing factor.

It was estimated that nearly two-thirds (64 per cent) of physical assault victims thought this was the case; as did more than half (57 per cent) of the victims of face-to-face threatened assault.

A Sunday Canberra Times analysis of 2011 crime data found that Canberrans were more likely to be robbed or assaulted in Civic or Belconnen than any other part of the city. Police recorded 343 assaults in the city centre last year.

Recently retired bouncer Zoran Matijevic, who spent more than a decade working in Civic, said many fights were being missed.

''[The stats are] very under, they're very, very well below,'' Mr Matijevic said.

''I think it would have to be close to double that number of incidents in the city.''