Thousands of people marched into Brighton city centre in a peaceful demonstration against Britain and America going to war.

About 8,000 people were expected to march against capitalism and globalisation at the start of the Labour conference in Brighton yesterday.

Torrential rain meant only an estimated 4,000 demonstrators joined the march from The Level to the conference venue, the Brighton Centre.

More than 780 police officers from Sussex, Kent, Hampshire, Dorset, Surrey, the Met and British Transport Police lined the route.

For the first time in a demonstration on mainland Britain, all officers on duty were issued with Captor pepper spray, which temporarily stuns the offender.

Tight security meant fears the event would be hijacked by extremists were unfounded.

Eight men, including three 16-year-olds, were identified as potential trouble-makers. Riot police officers walked into the crowd and arrested them. As they did so, some resisted and hit out.

Chief Inspector Robin Smith said: "They were singled out as the result of intelligence. They were arrested as a preventative measure to stop the possibility of trouble later on."

Police sealed off side roads, keeping the chanting marchers on the main roads to the seafront. Officers in riot helmets, some with dogs, prevented demonstrators from getting into the city centre.

Surveillance teams filmed the marchers who were channelled on to the south side of Kings Road as they approached the security barriers around the Centre.

Hundreds of police, including mounted officers, were stationed inside the secured island site that surrounds the conference venue.

Police spotters with binoculars scanned the chanting crowds for potential trouble-makers.

Supt John Bransfield estimated about 50 people were intent on causing trouble. A number of concealed weapons were confiscated.

One woman was treated by paramedics for a suspected overdose after collapsing outside the Brighton Centre. There were no other reported injuries to either police or marchers.

Demonstrators included a man dressed as a vicar, who danced in front of the march wearing signs reading "The end is nigh". Two women braved the rain to march topless with anti-war slogans written in lipstick across their chests.

Among the protesters were six students from Brighton, Hove and Sussex Sixth Form College (BHASVIC).

They marched under a banner which read: BHASVIC Students Say Drop Aid Not Bombs.

Peter Baker, 18, said: "We feel very strongly about how terrible war is and don't think the Government should be involved in dropping bombs on innocent women and children."

Fellow student Charlie Cairns, 17, said: "Capitalism means poorer countries suffer at the hands of the richer nations. All the money being used for weapons could be used to buy aid to feed the refugees from Afghanistan."

Brighton Green Party chairman Keith Taylor appealed for a peaceful demonstration before marchers set off. He told a rally of about 1,000 people gathered on The Level that the march had been organised before the terrorist attacks on the US on September 11.

He said: "It has brought a relevance and a sombre tone to this rally. We want Tony Blair to know that he does not have a blank chequebook for mass destruction.

"We don't want him to be able to use the excuse of crowd disorder to take the focus away from why we are protesting."

Protesters joined the march as it set off led by the Carnival Collective samba band from Shoreham Beach.

Ben Tweddell, from Elm Grove, Brighton, said: "I am here with my friends because we don't want to see a war being started."

After the march, Chief Insp Smith said: "The main aims of our operation were to allow peaceful protest, to prevent crime and disorder and to deal promptly with any offenders.

"It was a significant success which, early on, was contributed to greatly by the weather."

Guy Taylor, spokesman for one of the march organisers, Globalise Resistance, said: "It was a pretty good turnout considering the terrible weather."