Simon Calder, a travel journalist, says the disruption at London Paddington train station could continue into the weekend.
A number of services, including trains to and from south Wales, were cancelled after signalling problems caused major disruption to a line.
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Andrea Byrne presents the first episode of the new series Helimeds which follows the Welsh flying medics.
Variable cloud and clear spells overnight with isolated showers mainly in the north.
Becoming drier and brighter from the northwest during the day, but with the risk of scattered, locally heavy, showers developing later.