LONDON (AP) — British rail travel was returning to normal Friday afternoon after problems with a radio system used by drivers and signalers nationwide caused widespread disruption during the morning commute.

The fault led to “short-notice” delays and cancellations throughout the U.K., according to National Rail, which represents train operating companies. Lines affected included the Elizabeth Line serving London’s Heathrow Airport and the Gatwick Express to the capital’s second-biggest airport.

The issue mainly affected trains preparing to leave the depot at the start of their journeys, with services operating normally once they were underway, National Rail said. The problem was reported just before 6:30 a.m. local time and wasn’t resolved until 1:39 p.m.

“The fault meant that train drivers were having to manually log into the national radio network rather than it happening automatically,″ National Rail said. “The system is now working normally. We’re sorry if your journey has been affected today as a result of this issue.”