Millions of users across the United Kingdom are without a mobile phone signal as a nationwide outage hits millions.
The outage is preventing people from making phone calls or receiving them including emergency calls.
Anyone needing to contact emergency services is advised todo so via a landline phone.
O2 have reacted saying it was aware of “isolated instances” of intermittent service across the UK, and it was investigating the situation.
It is not yet known if emergency services radio networks are down, as these use the o2 network.
— Pauline (@PaulyP45) May 25, 2015