They hang out in a smoke-filled bar called La Dolce Vita, by the bridge. The irony is too heavy to miss because there is nothing remotely sweet about life in Mitrovica, the gritty mining town in northern Kosovo that has been divided between ethnic Serbs and Albanians since 1999 and this week, once again, is seething with tension.
They call themselves the Bridge Watchers. They are known for delivering the Kosovo Kiss – a sound beating, dished out to anyone who, in their view, pushes their luck. Some are veterans of Serbian paramilitary groups during the war, others are thought to be in the pay of political groups.
"They're the heavy boys," said one of their former victims.
On Thursday, a clump of them crossed to the approach to the bridge that crosses into the Albanian end of town. Shaven heads, sports jackets, intimidating bulk, beer bellies: they looked like old-time British skinheads gone to seed.
They stood in a huddle, chatting and joking – then suddenly span round and attacked a cameraman from Albanian TV. They beat him until he fell to the ground, then kicked him where he lay. He was taken away in an ambulance.
Yesterday, after the previous night's mayhem in Belgrade, tensions were even higher. There were persistent rumours that a force of neo-Nazis and ex-paramilitaries was on its way down from Serbia to Mitrovica and the Nato and Kosovo forces were prepared for just about anything.
The biggest crowd of the week had gathered up the hill from the bridge, in the main square of North Mitrovica and on the south side of the bridge, for the first time this week, a crowd of ethnic Albanian men had gathered to keep an eye on things. There was a heavy official presence too.
Five lines of police with batons and shields and automatic weapons stood guard outside the police station, while white Nato armoured personnel carriers and a platoon of French soldiers in fatigues stayed just out of sight. On the bridge itself, a band of riot police prepared to defend either end.
This week's protests have tended to start at 12.44pm in honour of UN Resolution 1244, the diplomatic clause that Serbia claims has been violated by Kosovo's independence.
At the due time, the Bridge Watchers huddled outside the La Dolce Vita. For more than an hour, nothing happened then, soon after 2pm, a large crowd came swarming down the hill from the main square on the Serbian side of Mitrovica, at least 5,000 protesters, banging drums, chanting "Kosovo is Serbia" and waving Serbian flags.
They got as far as the road near their end of the bridge, and, amid chants and piercing whistles, a volley of firecrackers rained down on the riot police.
But they came no further. The Bridge Watchers, apparently intermixed with Serbian police in plain clothes, had mutated into stewards, keeping the demonstrators on a tight rein. After half an hour, with no serious incidents or injuries (though one American photographer who was in the wrong place received the Kosovo Kiss), the protesters dispersed as suddenly as they had arrived.