Britons have been urged to "keep their cool" as a test of the national emergency alert system is set to take place on Sunday (September 7). At 3pm, mobile phones connected to 4G and 5G networks will vibrate and emit a siren sound for up to 10 seconds.

This will be the second test of the system, following the first in 2023. Mobile phone users will also receive a message clarifying that the alert is a drill.

The Government has used the system to issue real warnings five times, including in January during Storm Eowyn to alert people in Scotland and Northern Ireland about severe weather conditions. Approximately 3.5 million individuals across Wales and south-west England received an alert during Storm Darragh last December.

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