Network Rail has confirmed that floodwater is likely to continue to affect trackside signalling and safety equipment for some time.
In a statement, they said: "While they work to fix the problem we will only be able to run five trains an hour between Paddington and Reading in each direction. This is around a fifth of the services that would normally be scheduled.
"This will continue until Network Rail lets us know it is safe to run a full service again. We strongly advise customers not to travel unless it is absolutely necessary, and to consider alternative routes."
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Before the final declaration on Friday, the Conservative candidate looked set to lose the City Hall race to Labour's Sadiq Khan.
The Tooting MP has been the frontrunner in the counting process ahead of Tory challenger Zac Goldsmith.
It's not just London where elections have been taking place today. There were council elections taking place across the home counties.