Rail services on Britain’s main intercity lines were halted and passengers told of potential prolonged disruption ahead, after cracks were found on high-speed trains. All intercity trains on Great Western Railway and London North Eastern Railway were suspended on Saturday morning, as their entire fleets of Hitachi trains were taken out of service for safety. Urgent inspections were being carried out across the operators’ fleets after hairline cracks were discovered in several trains, with GWR trains suspected to be most affected. Ministers ordered a rapid review after the latest problem discovered in the Hitachi trains led to them being withdrawn from the network overnight on Friday, leaving thousands of passengers unable to travel on lines linking London to Scotland and to the south-west. Hull Trains and TransPennine Express, which also use similar Hitachi models, were disrupted, although their trains were being released back into service after inspection. About half of LNER trains had been passed fit by late Saturday afternoon. Hitachi said the problem on its Class 800 trains, which were commissioned by the government for GWR and the East Coast LNER services in a controversial £5.7bn order, was still under investigation. The cracks were found in the “lifting points” under the carriage – a new issue, after cracks were found in brackets linked to the suspension in GWR trains that were taken out of service in recent weeks. The rail minister, Chris Heaton-Harris, said routine checks had identified cracks on part of the chassis of some Hitachi trains. He said: “Safety is always our absolute priority, so these trains have been taken off the network to undergo full and rigorous checks. “Hitachi are working to complete these strict precautionary checks. Trains will be returned to service as quickly as possible once they are fully approved as safe by the manufacturer. “Whilst some trains are starting to be reintroduced, disruption is likely for a prolonged period, particularly on GWR. “We have also asked the industry to conduct a rapid and comprehensive review to resolve the issue.” LNER and GWR advised passengers not to attempt to travel on Saturday, although some services recommenced in the afternoon. All high-speed GWR services between London, Bristol, Cardiff and Penzance were originally cancelled. Among the affected passengers were Michelle Hammond, 38, an executive assistant from London, who had planned to travel with her husband and their 11-month-old baby from Tiverton Parkway in Devon to London on the 9.31 service. She said the live train trackers had not shown the cancellation: “It’s a disaster. We left home just after 8am and drove for an hour to the station, paid for our parking for the whole day, only to be met by a sign on the platform that told us the train was cancelled. It’s very frustrating, we’re massively out of pocket.” Roger Ford, the industry and technology editor at Modern Railways, said significant disruption was to be expected for a while, and that the latest development must have been serious to prompt the sudden withdrawal from service. The new fault is understood to be in a different part of the carriage from the problem discovered in April, when a crack of “substantial depth” was found during an inspection of one of GWR’s 93 Intercity trains. Ford said GWR would likely be more severely affected than other operators as it took the first deliveries of Class 800 trains – built in Hitachi factories in Japan and Italy, and now mainly assembled in the Newton Aycliffe plant in north-east England. The 65 trains used by LNER, branded Azumas by the operator, are newer. Ford said metal fatigue discovered in April that caused hairline cracks up to 15mm deep had seen some trains taken out of service for repair. “This is now a separate issue, a different part of the shell – but metal fatigue gets worse, the cracks get deeper, with age.” Hitachi Rail apologised for the disruption. A spokesperson said: ““We understand the frustration caused and we would like to apologise for the inconvenience caused to passengers and operators. “Having been cleared for service, some trains are now running again across the network. We are working as quickly and safely as possible to investigate the issue across the remainder of the fleets.” Unions called for a full investigation. Mick Lynch, general secretary of the Rail, Maritime and Transport union, said: “RMT is fully aware of the issues that have led to the cancellation of services on LNER today and that similar problems with cracks appearing in the fleet on Great Western are also emerging. “Hitachi needs to ensure the highest safety standards and properly investigate and rectify the issues.” TSSA general secretary Manuel Cortes said: “This rolling stock must not be allowed back into service until we are 100% certain these trains are safe.” The Hitachi trains suffered an embarrassing start in 2017, when the first GWR trains had to be taken out of service after a series of breakdowns, including on the inaugural service carrying the then transport secretary Chris Grayling from Bristol to London.