Cleaners on London Underground will go on strike today for 48 hours, in a row over an Olympic bonus payment.
Members of the Rail Maritime and Transport Union who are employed by private contractors will walk out at 5:30am.
They're set to mount picket lines outside tube stations in London - including Stratford, close to the Olympic park.
The RMT union has said it is balloting cleaners who clean the London Underground for strike action. The union says the cleaners, who work for the companies ISS and Initial, deserve a substantial pay increase as well as other benefits.