The UK Government will conduct a nationwide test of its Emergency Alerts system at 3 p.m. BST on Sunday, 7 September 2025. Around 87 million 4G and 5G smartphones will vibrate, emit a siren for roughly 10 seconds and display a message indicating the alert is only a test, even if the devices are set to silent. Officials say the exercise is designed to verify technical fixes after the inaugural national trial in April 2023, when an estimated 7 percent of compatible devices failed to receive the alert. Since then, the system has been used five times on a regional basis, including warnings sent to 4.5 million people during Storm Éowyn in January and to 3.5 million during Storm Darragh last December, as well as during the evacuation of more than 10,000 Plymouth residents when a 500-kilogram World War II bomb was removed in February 2024. The test forms part of a broader Resilience Action Plan unveiled by Chancellor of the Duchy of Lancaster Pat McFadden. The plan includes £1 billion for a new network of National Biosecurity Centres, £4.2 billion to bolster flood defences and the launch later this year of Exercise Pegasus, billed as the country’s largest pandemic-preparedness drill. A public information campaign will precede the September test, with targeted guidance for vulnerable groups such as domestic-abuse victims, who can opt out to avoid revealing concealed phones. Materials will also be provided in British Sign Language to ensure wider accessibility.