Devices will vibrate and make a siren sound for 10 seconds at 3pm, with message confirming alert is a test

At around 3pm on Sunday, 7 September, all 4G and 5G mobile phones in the UK will blare a 10-second siren blast and display a test alert from the Government.

At about 3pm this coming Sunday all 4G and 5G mobile phones in the UK will blare a 10-second siren blast and display a test alert.

Millions of phones will emit a siren sound and vibrate during the drill

It marks the second test of the national emergency alert system after the first in 2023