We Are Young Fun.
As up to 10,000 staff on the underground walkout from 5pm in a row over job cuts at ticket offices, a row over safety's kicked off.
London Underground denies claims from the union it's risking safety by using untrained staff to keep things moving.
Stay with London's Heart for updates on the strike and there's travel advice below:
London Underground will run as many stations as possible, but disruption is likely on most journeys.
Extra buses will be used on key routes to boost the capacity.
DLR, London Overground and Tramlink
Expected to operate as normal. Some stations where there is an interchange with the Tube may be affected.
Rail services are expected to run as normal and accept Pay As You Go Oyster cards.
Larger boats are being used to increase capacity on the river services. An additional 500 capacity shuttle service is also being provided between Tower, Westminster and London Eye Piers, which will operate 06.30 - 10.00 and 16.00 - 20.00 on Tuesday 7 September.
London Cycle Hire Scheme bikes will be available, but demand is expected to be high and bikes may be harder to find during the rush hour. Bikes can be left easily at the cycle parks at Finsbury Park and London Bridge