O2 network outage over as UK 4G restored

O2 customers can once again access mobile data services after the operator restored its 3G and 4G networks overnight.

The day-long O2 outage impacted all of the operator’s 25 million customers, as well as an additional seven million customers using Sky Mobile, Tesco Mobile and giffgaff, all of which use the same mobile infrastructure.

Customers voiced their frustration at being disconnected on social media, while the outage also affected businesses and other services such as London’s live bus arrivals timetable information.

O2 outage

“I want to let our customers know how sorry I am for the impact our network data issue has had on them, and reassure them that our teams, together with Ericsson, are doing everything we can,” said Mark Evans, O2 CEO, late on Thursday.

“We fully appreciate it’s been a poor experience and we are really sorry.”

O2’s 3G network was restored late last night, while 4G service resumed early this morning.

Issues were first reported at 05:30am on Thursday 6 December and it became clear the outage was the result of a glitch in software used by network equipment partner Ericsson and was affecting operators in other countries.

Ericsson confirmed the outage was caused by a node failure and appears to have been related to an expired certificate in the versions used by the affected operators.

“The cause of [the] network issue is in certain nodes in the core network resulting in network disturbances for a limited number of customers across the world, including in the UK,” said Marielle Lindgren. “The faulty software that has caused these issues is being decommissioned.”

O2 has said its technical teams will continue to monitor service performance closely over the next few days and that it will carry out a full review with Ericsson to determine how such a disastrous outage was able to take place.

Steve McCaskill is TechRadar Pro's resident mobile industry expert, covering all aspects of the UK and global news, from operators to service providers and everything in between. He is a former editor of Silicon UK and journalist with over a decade's experience in the technology industry, writing about technology, in particular, telecoms, mobile and sports tech, sports, video games and media.