UPDATE, 5.30pm: More than 20 Smash EDO protesters have been arrested today after up to 150 took to the streets to demonstrate.

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The protest against the manufacture of bomb release mechanisms at the EDO/ITT factory in Moulsecoomb kicked off at about 10am in Wild Park.

Sussex Police set up a designated protest area by the A27, but very few of the protesters used this.

Instead, they made their own way through Wild Park, along Lewes Road and London Road and into the city centre, clashing occasionally with police.

Brighton and Hove Divisional Commander, Chief Superintendent Graham Bartlett, says: "Officers have made significant arrests this afternoon in order to prevent a further breach of the peace.

"Despite designating a highly visible site for protestors on the main road to the factory, many of them have not used it.

"Our aim today was to facilitate peaceful protest, instead many have caused disruption by failing to comply with police directions, running away through fields and woodland and being a nuisance to local people by blocking main roads in the city.

"Their disorderly behaviour has put pressure on police resources as we have needed to contain them to curb further disruption as they have blocked roads and headed towards other targets in the city.

"Injuries have been caused by protestors running around. Police medics were quickly on hand to treat one woman who ran into railings and injured her knee before an ambulance arrived."

On several occasions, officers kettled, or contained, the demonstrators. The first kettle took place at Ivy House in Wild Park early in the morning, where about 40 protesters were ordered to remove their masks before being allowed out.

Officers said they asked people to remove the masks if it was believed they were being used to conceal protesters’ identities.

More kettles took place in Wild Park at about 11am, while more protesters ran into the Moulsecoomb Estate.

Early reports the factory had closed for the day proved unfounded. However, Lewes Road, Bear Road and London Road were closed at times throughout the day, with activists at one point taking barriers from nearby roadworks to obstruct Lewes Road.

The English Nationalist Alliance also came into the city centre, where leader Bill Baker said they would be drinking and taking pictures. No trouble has been reported in relation to this presence.

By 1pm, four arrests had been made, two for suspected theft after vehicle was stopped, one for having a bladed article and one for breach of peace.

Another arrest was made shortly afterwards in relation to a dispute between protesters and residents, and there were also reports of protesters fighting amongst themselves in London Road.

Shortly before 2pm, the bulk of the protest was kettled on the Lewes Road, and police then arrested those inside one by one, all for allegedly breaching the peace if they refused to give their identity.

According to independent legal advisors, about 35 people, including on of the advisors, were arrested. However, Sussex Police said the total arrests was nearer 20. All those arrested were still being held at 5pm and police said they would be released when the risk of further breach has diminished.

At 3pm, there was a small protest outside Barclays Bank in North Street, but by 4pm, despite a small presence near the factory, the protest had largely petered out.

Officers from neighbouring forces, who are the most expensive for Sussex Police to use, had already been stood down, and the force was looking to stand down more to reduce the cost of the policing operation.