Citizens of Britain are advised to remain calm during a trial run of the emergency alert system

The national emergency alert system in Britain will undergo a test on Sunday, 7th September, 2025, at around 3pm. This test is crucial to ensure the functionality and readiness of the public warning system for emergencies.

This is the second test of the system, following its first test in 2023. The system has already proven its effectiveness, having been used by the government five times to issue real warnings, including during Storm Eowyn in January.

During the test, mobile phones connected to 4G and 5G networks will vibrate and emit a siren sound for up to 10 seconds. Approximately 3.5 million people in Wales and south-west England received an alert during Storm Darragh last December, giving a glimpse of the system's reach.

The emergency alert system allows messages to be targeted to relatively small areas, pinpointing those at risk. This precision was demonstrated in May 2024, when approximately 15,000 phones were alerted during flooding in Cumbria. Similarly, 10,000 phones received a warning during flooding in Leicestershire in January this year.

Another instance where the system was activated was in February last year, when a warning was triggered by a 500kg unexploded Second World War bomb found in a Plymouth back garden, affecting around 50,000 phones.

In addition to mobile alerts, warnings would also be transmitted on television, radio, and locally by knocking on doors. The system is designed for use during the most likely emergencies to affect the UK.

Following the test, performance will be assessed with mobile network operators. The government has also met with domestic violence charities and campaigners for discussions on helping those who may need to opt out of the test. Mobile phone users will receive a message making clear that the alert is a drill.

The test is intended to ensure the system works well when needed most, keeping the country safe 24 hours a day, 365 days a year.

Citizens of Britain are advised to remain calm during a trial run of the emergency alert system