The first nationwide trial of the network, which aims to warn people of nearby danger such as flooding or terror attacks, will see devices sound an alarm and vibrate for about 10 seconds at 3pm on 23 April.

In response, play at the World Snooker Championship being hosted at the Crucible in Sheffield, will be temporarily suspended shortly before the alert and then resume afterwards.

The Society of London Theatre said it had advised its members to tell audiences to turn off their phones to "minimise disruption to shows".

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 performances.

For film-goers, a spokesperson for the Vue cinema chain 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."

The test on St George's Day coincides with major events including the London Marathon and the 2pm kick-off Premier League ties between Bournemouth and West Ham, and Newcastle and Tottenham Hotspur.

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 or switch off their phones completely, but the authorities hope many will choose to keep them on.

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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.

The government said it had engaged with domestic violence organisations to ensure vulnerable women and girls, who may have concealed second mobile phones, are not impacted by the alerts.

Motorists have been warned that it will be illegal to pick up their mobiles during the test.

Motoring groups have said drivers may want to switch off their devices before Sunday's test as laws banning the use of handheld phones still apply.

People caught holding a phone behind the wheel face six penalty points and a £200 fine.