The London Marathon may change part of its route on Sunday because of an ongoing protest by Sri Lankan Tamils at Parliament Square, the BBC has learned.
The protest has been taking place there since the beginning of April.
BBC London's political editor Tim Donovan said race organisers had been meeting because they feared disruption.
Police said there was no evidence protesters planned to interfere. The route may be moved from Parliament Square to Admiralty Arch instead.
No decision on a route change has yet been made, but Tim Donovan said the decision could be made on the day of the marathon.
Organisers could decide an alternative route as a precaution
Police said there had been no intelligence making disruption likely, but it was normal for plans to be made for alternative routes.
Last year, a gas leak forced organisers to change the route of the race only 20 to 25 minutes before the race started.
A London Marathon spokesperson said: "We are not actively considering re-routing the 2009 Flora London Marathon, which will take its traditional route on Sunday 26 April.
"During the event's history, the marathon has experienced minor gas leaks and fires, and have had to implement minimal changes to the route at short notice. As major event organisers we always have to consider potential causes for diversions that may be required on the day of the race and obviously have to have plans for such eventualities.
"Regular briefing meetings are held with all agencies involved with the London Marathon, including the Mayor's office, Metropolitan Police and other agencies."
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