Lines have fully reopened and services are returning to normal.
Rail passengers are facing delays of up to 40 minutes heading into London Paddington due to signalling problems between Maidenhead and Slough.
The signalling fault means trains have to run at a reduced speed on all lines heading towards Paddington.
Operator Great Western Railway is warning trains may be cancelled, delayed or revised.
Disruption is expected until noon.
Top Ten Articles
An extra £20,000 looks set to be allocated by the Royal Borough to fund a legal fight if Heathrow Airport is given permission to expand.