Signalling problems in Maidenhead have caused delays on rail services to London this morning.
Trains have to run at reduced speed on lines bound for the capital.
Services running through Maidenhead station may be cancelled, delayed by up to 30 minutes or revised at short notice.
First Great Western said at 8.37am that an estimate for the resumption of normal services will be provided as soon as it has fully assessed the problem.
Commuters were already facing disruption today after a 48-hour strike by underground staff started last night.
Visit the First Great Western website for updates.
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