Brits across the country launched into a panicked frenzy at 3pm as siren sounds blared from mobile phones.
The national emergency alert system sounded all roughly at the same time on Sunday for anyone whose mobile is connected to 4G and 5G networks.
Much to the panic of millions, the alarm consisted of vibration and sound for about 10 seconds in the second test of the system – after the first in 2023.
Sporting events reportedly had to adjust for the alert, with England’s third ODI cricket match against South Africa scheduled to pause and the kick-off for the Super League derby between Hull KR and Hull FC pushed back. Meanwhile, theatre-goers were advised to turn their phones off and drivers urged not to be distracted behind the wheel.
Mobile phone users received a message making clear that the alert was a drill.
The Government has used the system to issue real warnings five times, including in January during Storm Eowyn to warn people in Scotland and Northern Ireland about severe weather.
Approximately 3.5 million people across Wales and south-west England received an alert during Storm Darragh last December.
A 500kg unexploded Second World War bomb found in a Plymouth back garden triggered a warning to some 50,000 phones in February last year.
Messages can be targeted to relatively small areas to pinpoint those at risk.
Around 15,000 phones were alerted during flooding in Cumbria in May 2024, and 10,000 received a warning during flooding in Leicestershire in January this year.
The system is designed for use during the most likely emergencies to affect the UK and warnings would also be transmitted on television, radio and locally by knocking on doors.
Government officials also met with domestic violence charities and campaigners for discussions on helping those who needed to opt out of the test.