Emergency Alert: Millions of UK Mobile Phones to Receive Test Message on Sunday

The UK’s emergency alert system is designed to warn people if there is danger to life nearby, including outbreaks of extreme weather.

Millions of mobile phones across the UK will emit a loud siren sound and vibrate for 10 seconds this Sunday at 3pm as part of a nationwide test of the government’s emergency alert system. The message, which will appear on handset screens, will confirm that the alert is only a test.

With an estimated 87 million mobile phones in the country, a large portion of the population is expected to experience the alert. However, officials note that some devices—particularly older models and those not connected to 4G or 5G networks—may not receive it. Phones that are switched off or in airplane mode will also not sound.

A 10-Second Test Designed to Minimise Disruption

According to the government, the alert’s 10-second duration strikes a balance between conducting a meaningful test and minimising inconvenience. Despite this, some disruptions have already been felt: the Glasgow derby between Celtic FC Women and Rangers Women has been delayed to 3:05pm to avoid clashing with the alert.

Pat McFadden, a senior cabinet minister, described the alert system as a “national fire alarm”, emphasising the importance of regular testing.

How the UK’s Emergency Alert System Works

The national alert system is designed to notify people of nearby threats to life, including:

• Severe weather events

• Natural disasters

• Public safety emergencies

Since its launch in April 2023, the system has been activated five times, with the largest alert sent to 4.5 million people during Storm Éowyn in January. The first real-world use occurred in Plymouth in February 2023 when a 500kg World War II bomb was discovered and safely removed.

The alert system works by broadcasting signals from local mobile phone masts to all devices within range. This means that even tourists with international SIMs will receive the alert if they are in the affected area.

Opting Out and Domestic Abuse Concerns

The government has issued guidance for users who wish to opt out, noting that victims of domestic abuse with hidden phones may need to disable alerts for safety. Importantly, switching a phone to silent will not block the alert. The only guaranteed methods to avoid it are:

• Turning the phone off

• Keeping it in airplane mode

Even then, devices switched back on shortly after the test may still receive the message.

Past Issues and Improvements

During the first nationwide test on 23 April 2023, around 7% of devices failed to receive the alert due to network-related issues—affecting an estimated 5 million phones. The Cabinet Office, however, deemed the trial successful, stating that all identified problems were resolved within a week.

Preparing for a More Volatile Future

The National Preparedness Commission (NPC), which promotes readiness for major national risks, welcomed the test as an essential part of strengthening the UK’s resilience.

NPC Chair Toby Harris stressed the urgency of preparedness given:

• Recent defence and security concerns

• Increasingly extreme weather

• A more unpredictable international environment

“The need for this sort of preparedness is becoming even more important,” Harris said.