GWR is taking urgent measures and other operators have stepped in to help passengers caught up in rail chaos after cracks were found in high-speed trains.

The company's managing director Mark Hopwood has written a reply to West of England metro mayor Dan Norris who demanded to know what it was doing to get people onto services amid a raft of cancellations across the region.

Mr Hopwood said the withdrawal of Hitachi's entire 800 Series trains, including the vast majority of GWR's Intercity Express fleet, from Saturday morning had a "very significant impact" on long-distance routes, with passengers urged not to travel.

Rail journeys to and from Bristol Temple Meads and Bristol Parkway are among those worst affected, although Mr Hopwood said 85 per cent of GWR services were local, regional and branch lines and were not impacted.

He said: "The railway industry has come together to help support services and our customers, with other train operators allowing our customers to travel on other routes, such as Crosscountry services into Bristol.

"Crosscountry have also added additional shuttle services to help us move customers between Bristol and Didcot to connect with services into Swindon and beyond."

Mr Hopwood said GWR had also obtained permission to bring its Thames Valley electric fleet to Swindon, which came into service today (Wednesday, May 12).

"This required some staff training, which we are now completing," he said.

"As you note in your letter we are now looking at what other options might be possible including bringing in trains from other areas.

"We have brought more staff into stations and onto our social media platforms to help with advice.

"Details of the revised timetables are entered into journey planners by Network Rail overnight and are in place for customers to check journeys before they set out.

"We are also providing updates on our website www.gwr.com and have extended ticket validity so that tickets can be used at any time this week, or next weekend.

"We do understand how difficult this is for our customers and we are looking at every possible option to help reduce the impact."

He suggested a virtual three-way meeting with Mr Norris and Hitachi UK lead Jim Brewin to provide the mayor with updates on plans to get the high-speed trains safely back into service.