Huge travel disturbance is expected on trains in Wales on Saturday as services between Swansea and London have been cancelled due to “precautionary checks”.
National Rail has confirmed that there is “major disruption to Great Western Railway services today”.
A number of services have already been affected, with operators urging people to check their journeys before travelling.
The issue with a number of trains is being investigated but there is no indication yet as to when the problem will be rectified.
According to National Rail, there will be “no train services or alternative means of transport available for throughout journeys in either direction” on the following routes:
Customers intending to travel on these routes are advised not to travel.
A spokesman for Great Western Railway said: “A number of Class 800 series Hitachi trains from several train companies have been taken out of service today for checks as a precautionary measure.
"This problem is being investigated by Hitachi and once trains have been checked, we hope to be able to release them back into service as soon as possible.
“This will affect a significant number of today’s Intercity services and local lines are also likely to be extremely busy. Customers are advised not to travel. Refunds will be provided and customers should visit gwr.com for more information.”