The Carabinieri, whom Manchester United fans will witness in numbers tonight, are technically a military corps but are used in general police work. Equipped with long batons, full-face helmets and teargas guns, they share the job of football security with units of the state police.

In July 2001, at the G8 summit in Genoa, the Italian police earned a reputation for brutality after they clashed violently with anti-globalisation protestors. Their heavy-handed response, which led to a large number of officers being charged with complicity to harm protestors, may have been justified by reports that they received direct instructions from the Interior Ministry to neutralise the protesters with the utmost severity.

With football the situation is very different. Hooliganism seems to enjoy a kind of diplomatic immunity. Football clubs have enormous influence, both economic and political, and local and national government appear unwilling to antagonise what are perceived as large sections of the population by clamping down. When violent fans are brought to court, they receive very light sentences, if any.

Some police openly confess their dislike of the job. When Middlesbrough fans were confronted by “Ultras” before their Uefa Cup clash with Roma last year, one Carabinieri officer confided: “We hate doing football matches. You see those s***s on the bridge? They didn’t come to see the match. They came to hunt the English. And they came to fight us.” Up to a thousand police can be on duty at matches, but they are invariably on the defensive. A few are inside the stadium, but most are outside, where the violence usually explodes. In some cases, fans of rival teams have joined forces to attack the police.

Tactics have often come under fire. The police usually stand in ordered double or triple lines facing the area where the most threatening “Ultras” are milling around. When the “Ultras” become particularly threatening, or when they start setting fire to rubbish bins or fighting in large numbers with rival fans, the police charge with batons, sometimes after firing teargas. The result is a chaotic mêlée in which anything can happen. During an incident in Catania after a Serie A match in February, a policemen was killed after he was cut off from his colleagues and attacked.

Critics of these tactics talk of prevention and intelligence as alternatives, but have come up with few effective solutions given the almost total freedom from punishment of violent fans.