GREAT WESTERN and Heathrow services are still disrupted this morning after an empty unit became derailed on the station throat last night.
GWR said track and overhead equipment had been damaged by the incident, although no one was hurt.
All services came to a halt last night, but four of the six lines had been opened by around 08.00 today.
However, GWR warned that 'significant disruption' would continue today while the track is cleared and repaired.
Some suburban services from the outer Thames Valley are terminating at Reading, and there are no Heathrow Connect trains. Other services to Bristol, south Wales and the west of England are also reduced, with some trains cancelled.
An investigation into the cause of the low-speed derailment has been launched.