Reclaim the Streets, the group behind the City of London demonstrations in June that resulted in battles with police, are holding the protest at Euston station. The group are demonstrating against the privatisation of the rail system.
There is concern that extremists at the 5pm rally, "Reclaim the Railways", could attempt to disrupt the transport system during the peak hour.
Sir Paul Condon, the Metropolitan Police Commissioner, said undercover detectives and hidden police camera crews would be part of the elaborate containment plan. At a briefing, he predicted the demonstrators would set out to obtain "maximum publicity and maximum disruption". The police are trying to guard against a repetition of the June demonstrations that began peacefully but ended in 28 officers and 14 members of the public being injured and hundreds of thousands of pounds worth of damage.
Police have since arrested 85 people and are seeking a further 130 who were filmed carrying out attacks.
Protesters tomorrow are expected to move from outside Euston station to Canada House to demand Canada withdraws its attempt at the World Trade Organisation meeting in Seattle to have the UK ban on asbestos imports lifted.