The government has released further details about next week’s UK-wide test of an emergency alert system.
A message will appear alongside a loud alarm on millions of mobile phones at 3pm on 23 April.
The text that will appear has now been revealed – and it will say: “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.
Phone users will be prompted to click “OK” on their home screen or swipe away from the message before being able to continue using their device.
Drivers are advised not to look at their phones until it is safe to do so.
The emergency alert system is intended to be used in life-threatening situations including flooding and wildfires.
It is modelled on similar schemes in the US, Canada, Japan and the Netherlands.
Oliver Dowden, chancellor of the Duchy of Lancaster, said: “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.”
But domestic violence campaigners have said the test could put people in danger by revealing the location of secret phones hidden away by those at risk.
The government said it has been engaging with organisations working with vulnerable women and girls to ensure they are not adversely affected.
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Officials said people can opt out of the system if they need to conceal their phones, either by turning off emergency alerts in their settings or simply having the device switched off during the test.
Several major events are taking place on the test day including the London Marathon and the 2pm kick-off of Premier League ties between Bournemouth and West Ham and Newcastle and Tottenham Hotspur.
The government said it has worked with the Football Association and the marathon’s organisers to limit the impact of the text.
Chief fire officer Alex Woodman, from the National Fire Chiefs’ Council, said: “We must use every tool at our disposal to keep people safe and we need everyone to play their part, and the new Emergency Alerts system is one way we can do this.
“For 10 seconds, the national test may be inconvenient for some but it’s important because the next time you hear it, your life, and the life-saving actions of our emergency services, could depend on it.”