O2 has pointed to a network hardware failure for an outage that blocked users in major UK cities from accessing mobile services on Monday.
Business and consumer customers across the country - including London, Manchester, Leeds and Newcastle - were unable to make calls or access 3G services for seven hours due the fault. The issue was identified and fixed overnight.
O2 said that the problems were not related to any system upgrades over the Bank Holiday weekend, and were instead due to a series of hardware failures.
“The problem was caused by some network equipment that was temporarily unable to correctly process mobile phone traffic for some of our customers,” a spokesperson told ComputerworldUK.
“To be more specific, it was primarily the system that allows overseas customers to roam onto our network. The problem also impacted a second piece of equipment that allows calls, texts and data for UK customers to be managed correctly on our network.
“Having identified this, we have now isolated the problem to prevent this from happening again.”
However, the company was unable to say why backup systems failed to kick-in to ensure service continued.
O2 customers vented their frustrations on social media on Monday, with the Government's business secretary, Sajid David, also complaining about the service, tweeting: “No signal @O2. Please sort it out.”
O2 subsequently apologised to customers before the service resumed at 11.35pm on Monday.
A statement read: “Yesterday afternoon some customers experienced a problem accessing our network and we apologise for the inconvenience caused to those customers who were affected.”
The company downplayed the effects of the network failure, claiming it was not on the level of previous network outages. Problems were experienced in 2012, for example, which led to the company upping its technology spend and replacing some core Ericsson systems.
Speaking at the time, o2 chief operating officer, Derek McManus, said: “We are removing the Central User Database provided by one of our suppliers, which has suffered two different faults in the last few months. We are not prepared to risk this happening to our customers for a third time and are implementing a proven alternative solution.”
A spokesperson said that previous service issues are entirely unrelated to the outage this Bank Holiday weekend.
O2 has recently been sold by parent company Telefonica to Hong Kong conglomerate Hutchinson Whampoa, which also owns mobile network provider Three, in a £10 billion deal.
Last year O2 highlighted its desire to expand its business from supplying call, text and data services to the more lucrative area of IoT, supporting connected devices and offering underlying services.