Rail passengers across Britain face disruption due to a fault with a radio system used by train drivers and signallers.
The National Rail Enquiries website said trains “across the network” are having to start their journeys later because of the failure of the onboard GSM-R system, and “may be subject to cancellations or alterations”.
South Western Railway is among the operators to cancel some services.
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It said in a message to passengers: “We have been informed of a national issue with communication systems affecting service this morning.
“This means that trains may be delayed before they start their journey.
“This is because it is preventing our train drivers from contacting the respective signalling centre this morning and a reset is having to be performed before the train can start its journey.”
Elizabeth line trains serving Reading and Heathrow airport are also affected.
ScotRail passengers are being permitted to travel via “any reasonable route” because of the issue.
Gatwick Express, Great Northern, Southern, Thameslink and Southeastern services are also disrupted.
The failure with the GSM-R system “is currently being investigated”, National Rail Enquiries said.
GSM-R is designed to enable driver and signallers to communicate digitally at all times, including while trains are in areas such as tunnels and deep cuttings where previous analogue systems did not work.
It was rolled out to increase safety and reduce costs by replacing the patchwork of inefficient legacy systems which were expensive to maintain.
A Network Rail spokesperson said: “We have discovered a fault with the railway’s radio communication system that is preventing it from automatically ‘logging on’.
“The back-up manual log-in system is being used instead, causing a few minutes of delay at the start of the day.
“Once up and running the system is working normally and the impact for passengers is minimal.”
