Police have arrested 53 men, believed to be supporters of the English Defence League, who were heading to London.
The men were held on the M25 motorway near Heathrow Airport and Uxbridge and on the M3 near Bagshot, Surrey, on Saturday afternoon, police said.
The men were heading to a location in east London, but police have not revealed where they were due to gather.
All 53 were arrested on suspicion of conspiracy to cause public nuisance, the Metropolitan Police said.
They have been bailed until a later date pending further inquiries.
A Met spokesman said: "This was part of an intelligence-led investigation into a planned disturbance in east London on that day (Saturday)".
One of the bail conditions imposed on the men bans them from entering east London to demonstrate for a stipulated period of time, police said.
The men were taken to police stations in central and south London.