There is disruption on First Great Western between Worcester Shrub Hill and Swindon, and between Worcester Shrub Hill and Oxford because of a derailed train.
Some lines are now blocked as the train is re-railed which could take up until 2.30pm.
Replacement buses are running between Worchester Shrub Hill and Cheltenham and journeys will be delayed by up to half an hour.
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The government is consulting on proposals to introduce an hourly fast train in parts of the south east - not stopping at some stations
Monday night's forecast for the west of the region
Monday night's forecast for the east of the region