Far right activists are to protest in the capital after ignoring moves by police and the Home Secretary to stop them.
The English Defence League has told Scotland Yard it is leading a "static" demonstration in the wake of Theresa May's 30-day ban against marching in six areas.
More than 3,000 officers will be available on Saturday amid fears of violence and clashes with opposition groups, including Unite Against Fascism.
Campaigners have been in ongoing negotiations with police chiefs in the wake of tough measures introduced by Mrs May.
It is the first time since the Brixton riots 30 years ago that police have requested powers to stop marches in London.
Chief Superintendent Julia Pendry said: "Following the appalling disorder in London in recent weeks, it's important London, its communities and businesses, can return to normality."
While concern of unrest centres on the deprived inner city borough of Tower Hamlets, Mrs May also banned marches in Newham, Waltham Forest, Islington, Hackney and the City of London amid fears that demonstrations could spill across the border.
A message posted on the EDL website said a demonstration in Tower Hamlets is definitely going ahead. "We will gather at muster points, and then be escorted to the demo site by the police," leaders said.
The RMT transport union attacked the EDL for claiming a strike on the Tube's Central Line has led to the cancellation of the EDL's operational arrangements in London.
A spokesman for the union said: "At no time has RMT talked about a strike - this is a clear cut safety issue for our members who have already had experience in the past of EDL mobilisations. It is our union's duty, and we believe the employers, to protect our members' safety at all times."