Sean Dilley
Transport correspondent

The BBC understands that the cause of a nationwide delay to train services across Britain lies within an on-board communication system known as the global system for mobile communications – railway (GSM-R).

The technology uses digital communications between trains and signallers to improve safety for passengers.

While it works in a similar way to mobile phones, the digital system is not reliant on commercial mobile phone operators. The rail network has its own contained phone and mast system.

One rail source told the BBC that “the system isn’t connecting easily”. There is a workaround that staff can use but it takes time.

We’ve also been told that once the system is operational “there are no problems”, but investigations are underway in to why the GSMR network is experiencing problems.