Trouble flared at Drumcree yesterday afternoon when scores of protesters, some in Orange Order regalia, attacked police and British soldiers with stones, bricks and bottles.
One man was removed to hospital in an ambulance after a plastic bullet struck him on the arm, and 24 members of the Police Service of Northern Ireland were reported to have been injured. Nine of the officers received hospital treatment, and two were detained. A number of other injuries were also reported.
Three people were arrested for riotous behaviour, and further arrests are expected after police have studied video footage of the incidents. The police used water-cannon at one stage to prevent about 150 demonstrators from tearing down barbed wire close to Drumcree bridge.
Police described the violence as "brutal" and "vicious".
The parade to Drumcree passed off peacefully. However, as the crowd was about to disperse, some protesters started tearing down the security barrier at the bridge, which was a smaller fortification than in previous years.
At that stage the annual Somme service at Drumcree church had concluded and the speeches outside the church had also finished.
The first hint of trouble came when senior Orange Order officials made a formal protest at the security barrier over being banned from parading down the Garvaghy Road. They handed a letter of complaint to an Assistant Chief Constable, Mr Stephen White, who, with a number of his officers, was spat upon by some of the protesters when he came through the barrier to meet the Orange officials.
Shortly afterwards the demonstrators started tearing down the barrier and throwing missiles at the security forces. Police and troops in riot gear then moved in to erect a larger barrier.
Protesters at the scene, some wearing Orange Order collarettes, attacked the security forces with bricks, stones and bottles. Three plastic bullets were fired during the ugly scenes, and the area remained tense for about an hour, after which most of the crowd started to make their way home.
The violence will prove embarrassing for the Orange Order, which had urged troublemakers to stay away from Drumcree. The embarrassment is exacerbated by the fact that some of the order's own members were directly involved in the disturbances.
Before the trouble, the indications had been that the day would pass off without any major incidents. There was not the same tension in Portadown town centre as in previous years when the parade to the church moved off. About 1,000 Orangemen marched to Drumcree church, and hundreds of their supporters joined them there. This was in contrast to some of the worst years, when thousands of people gathered on the hill.
It was also evident that most loyalist paramilitaries had observed their pledge to keep away from Drumcree, again raising expectations that there would be little trouble.
Before the violence flared, Mr Harold Gracey, the Portadown district master of the order, who is in failing health, briefly addressed the crowd. "We are still here on this hill night after night, Sunday after Sunday, and we will continue to be on this hill until this problem is resolved," he said.
Mr David Burrows, Portadown deputy district master, said that the "naked sectarianism" young Catholic schoolgirls had experienced at the Holy Cross primary school in Belfast was similar to what Portadown Orangemen were suffering in being prevented by nationalists from parading down the Garvaghy Road.
"How pathetic that they lack so much confidence in themselves that they cannot spare us a few minutes of Christian tolerance while we walk home," Mr Burrows said.
"And make no mistake about it, what they're doing is not nationalism, it's fascism; the same sort of fascism that saw Nazis imprisoning Polish Jews in the Warsaw ghetto during the war; the same sort of paranoid fascism that made the apartheid regime confine the blacks to the shanty towns of South Africa."
Later, when the trouble broke out, Mr Burrows appealed for calm. "At the end of the day this does not help our cause. Everyone here can see that, and the whole world can see that. But we will not walk away from our responsibilities," he said.
The situation remained calm on the Garvaghy Road. A small group of nationalists gathered outside St John's Church in the morning as the parade went by without incident.
Mr Breandán Mac Cionnaith, the spokesman for the local residents, said he hoped that the Orange Order would disperse from Drumcree and not allow the protests to "drag out" over the coming days.
He said he was still prepared to discuss the parade with the order to see if there could be a resolution to the annual Drumcree protests.