Thousands of commuters face severe disruption on their journeys home tonight, because of problems with overhead wires at Radlett in Hertfordshire.
Three train companies have been affected - Southeastern, East Midlands and First Capital Connect.
Trains are unable to run between St Pancras International and Luton on East Midlands services.
First Capital Connect is also suspended between West Hampstead and Bedford.
And Southeastern trains are suspended between Denmark Hill and Kentish Town.
More top news
Olympic Park bosses have agreed to pay contractors an extra £36m to strengthen the roof.
Traffic was being redirected around part of the tree but pedestrians were allowed to continue walking past.
Friends of a woman killed by a falling tree during yesterday's storms have spoken of their shock at the tragedy.