At 3pm today every mobile phone in the UK will ping with a warning as part of a test of a new public alert system by the Government.
The new system mirrors existing schemes in countries such as the US and Japan and alert people in life-threatening situations such as floods, wildfires and other extreme weathers.
The warning will make a loud siren-like sound, even on devices set on silent or aeroplane mode, and also vibrate and read out the alert.
Ministers have described it as “the sound that could save your life”.
The text will read: “This is a test of Emergency Alerts, a new UK government service that will warn you if there's a life-threatening emergency nearby.
"In a real emergency, follow the instructions in the alert to keep yourself and others safe.
"Visit gov.uk/alerts for more information.
"This is a test. You do not need to take any action."
The message will be received on 4G and 5G mobile phones, along with sound and vibration for up to 10 seconds even if devices are on silent.
Drivers are advised not to look at or touch their phone until it is safe, just as when receiving any call or message.
A number of charities have also raised concerns that the upcoming nationwide emergency alert test could reveal such devices to their abusers, putting them in danger.
Among those was Refuge, which warned: “Refuge has concerns about the soon to be tested government Emergency Alert system, particularly the risk to survivors of domestic abuse who may have secret or secondary phones hidden within the home."
Officials say people can opt out of the system should people need their phone to stay concealed by turning off emergency alerts in their settings or having their phones off during the test.
On an iPhone, to turn the alert off, go into settings, open notifications, and scroll down to the bottom and disable the Extreme and Severe Alerts option.
On an Android phone, simply search your settings for emergency alerts using the search icon.
Chancellor of the Duchy of Lancaster Oliver Dowden said: "At 3pm next Sunday we'll be doing a nationwide test of our new Emergency Alerts system.
"Getting this system operational means we have a vital tool to keep the public safe in life-threatening emergencies.
“It could be the sound that saves your life."
