Overview

• The Cabinet Office has confirmed the nationwide drill will start at 3 pm on Sunday, September 7, sending a ten-second siren, vibration and on-screen test message to about 87 million compatible mobile devices.
• Alerts are broadcast over 4G and 5G networks to ensure high-priority delivery even under network congestion and will override silent modes.
• Since the first national test in April 2023, the system has been deployed five times in emergencies ranging from Storm Darragh and Storm Éowyn to flooding and a Second World War bomb operation in Plymouth.
• Ahead of the test, the government is running a public information campaign targeting vulnerable groups, providing guidance on device compatibility and opt-out procedures.
• The drill coincides with publication of a new Resilience Action Plan that invests in telecom security, flood defenses and data-sharing across devolved administrations to strengthen national preparedness.