An 80-year-old man was among four protesters arrested at a march that brought Brighton city centre to a standstill on its busiest day of the week.

John Catt, from Withdean, a veteran campaigner, was arrested after scuffles broke out at Saturday's demonstration against a factory which makes bomb release components for warplanes.

Protester Chris Osmond, 26, of London Road, Brighton, one other man and a woman were arrested for public order offences during the demonstration.

More than 50 police officers closed off North Street for the Smash EDO protest, which caused traffic chaos for an hour.

Police said they could not let the demonstration move through town because they had not been given a planned route in advance.

Superintendent Kevin Moore said: "Despite the efforts of the local police, no organisers for this event came forward to discuss their intentions on the day."

Protester Lorna Marcham, 20, from Southampton, said: "I think the police were completely over the top. Had they let the demo proceed down the street it wouldn't have caused any disruption.

"We don't liaise with the police because they just use the information to stop us more effectively."

The protesters, ranging from mothers with children to elderly people, gathered in Churchill Square at noon to hear speeches and hand out leaflets to passers-by.

The demonstration began moving down North Street at about 12.20pm but was blocked off into a side street by three lines of police.

Scuffles and struggles broke out when police locked arms to move protesters on to the pavement and four people were pulled out and arrested.

Crowds of shoppers lined the streets to watch as protesters chanted and jeered at the police.

Eventually they were allowed to filter down Windsor Street and by 1.15pm the streets were back to normal. About ten protesters made their way to The Level to continue their protest.

This was the third demonstration since an injunction was granted against Smash EDO last month under a law usually applied to stalkers.

Under its terms, campaigners are allowed to demonstrate at any time in any numbers but are not allowed to enter an exclusion zone around the EDO/MBM factory in Home Farm Road, Moulsecoomb, Brighton.

Supt Moore said: "Smash EDO are deliberately evasive in discussing their intentions with us.

"Today, the protesters' agenda was not about lawful protest for their cause. This was solely about bringing disruption and inconvenience to the city."

The march heralded the start of a peace camp at Wild Park in Moulsecoomb that will continue until Friday.