Mobile phone provider O2, has apologised to its customers after several parts of the UK including London, Glasgow, Manchester and parts of Northern Ireland lost signal. However they have said that service is “back to normal” and that an investigation into the problem has been launched.
In a statement, a spokesman said that service had returned to normal at 23:35 on Monday.
He added: "We apologise for any inconvenience caused to those customers affected and we will now begin a full investigation to identify the root cause."
Customers of the mobile provider took to social media such as Twitter to complain about the problems they were having.
Matthew Howett, a media and technology analyst told BBC Breakfast the fact that O2 had advised customers to turn their phones off and on again suggested "a problem with registering with the network".
He said while it was still unclear what had caused the issue, "a piece of software not doing its job properly" could have been to blame.
