Trains have returned to normal following a morning of disruption caused by a fault with a radio system.

Services “across the network” had to start their journeys later because of the failure of the onboard GSM-R system, causing delays and cancellations.

Southeastern was among the operators to have experienced delays to its services since about 6am.

Shortly before midday, the operator confirmed services were returning to normal following the issue - which was affecting communication systems between train drivers and signal operators.

A statement read: “Trains are returning to normal following a fault with the radio between signallers and our trains this morning.

“If you were delayed by 15 minutes or more, remember to claim Delay Repay.”

Gatwick Express, Great Northern, Southern, Thameslink, alongside Elizabeth line trains serving Reading and Heathrow airport, were among the services affected.

A Network Rail spokesperson explained this morning: “We have discovered a fault with the railway’s radio communication system that is preventing it from automatically ‘logging on’.

“Once up and running the system is working normally and the impact for passengers is minimal.”

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.