'Severe disruption' to First Great Western rail services
A signal problem in Berkshire led to widespread disruption to train services between Bristol, Swindon, Reading and London Paddington earlier.
First Great Western said the now-fixed signalling problem was in the Twyford area between Reading and Maidenhead.
Train services had been cancelled and seriously delayed by the fault but are starting to run again.
The train operator said it hoped normal services would be provided as soon as possible but warned of delays.
All lines between Didcot Parkway and Reading have reopened after commuters had been forced to travel on replacement trains.
First Great Western said it hoped normal services would be provided through these stations as soon as possible but delays were likely.
Trains are now running between Reading and London Paddington.