Millions of mobile phones will vibrate and make a siren sound across the UK on Sunday afternoon during a test of a nationwide emergency alert system.
Handset users will also receive a message on their screens reminding them the 10-second alert, which will happen at 3pm, is a test. There are about 87m mobile phones in the UK.
The government has said not all devices will receive the alert, including older phones and those not connected to 4G or 5G networks. The alert will not work on a phone that is switched off or in airplane mode.
The 10-second duration has been designed to “balance the need for comprehensive testing with reducing inconvenience to the public”, according to the government.
There has already been some disruption already, however, withthe Glasgow derby between Celtic FC Women and Rangers Women’s FC has been pushed back to 3.05pm on Sunday to accommodate the alert.
This week Pat McFadden, a senior cabinet minister, described the system as a “national fire alarm” that needed regular testing.
The UK’s emergency alert system is designed to warn people if there is danger to life nearby, including outbreaks of extreme weather in specific areas. It has been deployed five times since the first test in April 2023, with the largest use in January this year when 4.5 million received an alert during Storm Éowyn.
The first non-test use of the system was in Plymouth in February last year when a 500kg second world war bomb was discovered in a back garden – and safely removed by bomb disposal experts.
The government has also published advice for opting out of the alerts, acknowledging that victims of domestic abuse with a concealed phone might want to block the test. However, switching your handset to silent will not prevent the alert.
The alert will not sound if users have their phone switched off or if it is on airplane mode. However, if you turn your device back on shortly after the test, you might still receive the alert. The system works by broadcasting from mobile phone masts in a specific area, alerting every phone switched on within that radius – so tourists with non-UK numbers will also get the alert, for instance.
The first alert test on 23 April 2023 did not reach an estimated 7% of devices, according to the Cabinet Office, which nonetheless declared the trial “successful”. Some mobile phone users said at that time that their devices had not sounded, with the problem traced to specific networks including Three. The government estimated at the time that 5m phones had been affected.
A government spokesperson said problems with the last test were “all resolved within a week of the test being run”.
The National Preparedness Commission, an independent body that promotes policies helping the UK recover from significant shocks, said the test was an important part of the country’s preparations for threats ranging from extreme weather to national security challenges.
The NPC’s chair, Toby Harris, said: “Given what we have got with the strategic defence review, the increasingly volatile and worrying international situation, plus increasingly extreme weather events, the need for this sort of preparedness is becoming even more important.”
