Spectators of sport and entertainment may face disruption on Sunday when millions of mobile phones across the UK will emit a loud alarm and vibrate at 3pm in a nationwide test of a new public alert system.
The trial of the system that aims to warn the public if there is a danger to life nearby will last for about 10 seconds.
The system is intended to be used in life-threatening situations including flooding and wildfires.
Organisers of the World Snooker Championship will pause play just before 3pm at the Crucible in Sheffield and it will resume following the alert.
Harry Potter And The Cursed Child, Frozen, Mamma Mia! and The Lion King are among the shows putting on matinees on Sunday.
LW Theatres, Andrew Lloyd Webber’s group of seven West End theatres including the London Palladium, said it planned to make an announcement before its shows but had no plans to change the times of its matinee performances.
For cinema-goers who may be catching a film on Sunday afternoon, a Vue spokesperson said: “Before every screening at Vue, we encourage our customers to turn their mobile phones off in order to fully immerse themselves in the big screen experience.
“Customers who are attending a screening on Sunday afternoon will be further made aware of the UK emergency alerts test through signage in our venues and announcements before the films being shown over that period.”
Meanwhile, drivers have been warned that it will be illegal to pick up their mobiles during the test, and domestic violence campaigners have warned the test could put people in danger by revealing the location of secret phones hidden by those at risk.
The message will be received on 4G and 5G mobile phones, along with sound and vibration for up to 10 seconds.
Phone users will be prompted to acknowledge the alert by swiping or clicking the message before being able to continue using their device.
The system is modelled on similar schemes in the US, Canada, the Netherlands and Japan.
Officials said they have worked with the Football Association and the marathon’s organisers to make sure the impact of the test will be limited.
People who do not wish to receive the alerts will be able to opt out in their device settings, but officials hope the life-saving potential of the messages means that users will keep them on.
The National Centre for Domestic Violence (NCDV) warned people with hidden second mobile phones to turn off the alerts to avoid revealing the location of their devices.
The Government said it has been actively engaging with organisations working with vulnerable women and girls to ensure they are not adversely affected by the introduction of emergency alerts.
Officials stressed that it is easy to opt out of the system if people need their phone to stay concealed, either by turning off the alerts or simply having the phone switched off during the test.
The AA said motorists may prefer to switch off their electronic devices before Sunday’s test as laws banning the use of handheld phones will still apply.
Drivers caught holding a phone behind the wheel face six penalty points and a £200 fine.