The alert system is based on existing systems in the United States, Canada, the Netherlands and Japan. It will allow messages to be sent to mobile phones to quickly warn the public in case of danger.
Motorists have been warned not to pick up their phones during the test. London theatres had to ask spectators to turn off their phones so that the alarm would not sound in the middle of a show. The Daily Mail ran a headline: "What genius thought it was a good idea to terrify the whole country on Sunday?"