Emergency alert: Reports of 'scary' alarms at 1am on Monday after patchy trial

The government's first emergency alert test didn't go entirely to plan - with some mobile users claiming they were sent the foghorn-like blast in the middle of the night.

The alert was intended to reach people's phones at 3pm on Sunday, but some said they received it a minute early, others half an hour late - and many said they didn't get sent it at all.

But by far the most bizarre were the people who reported being sent the emergency alert in the middle of the night on Sunday or as a Monday morning wake-up call, with one commenting on Twitter: "That scared the sh*t out of me".

"Cheers @GOVUK for the Monday morning #emergencyalert," another added.

Read more: Emergency alert: Why did phone users get test at different times

Others reported that they also received the emergency alert on Monday morning - for the second time, having also been sent it on Sunday afternoon as planned.

Another said he got the alert twice - once at 1.21am.

"Just had another severe emergency alert on their phone? 8.15 am Monday 24 April. #severeemergencyalert #Alert," wrote one user.

Among the mobile phone users who said they did not receive any alert at all were those on the Three Mobile network, which is one of the biggest networks in the UK.

"We're aware that a number of customers have not received the test alert. We're working closely with the government to understand why and ensure it doesn't happen when the system is in use," the company said following the alert.

The exact timings of the alerts depended on operators' networks, which all have different speeds, the UK government said, explaining the alert was set to be "around 3pm" rather than hitting everyone's phones at the exact same time.

A UK government spokesman said: "We have effectively completed the test of the UK-wide Emergency Alerts system, the biggest public communications exercise of its kind ever done.

"We are working with mobile network operators to review the outcome and any lessons learned."

Communications professor Nigel Linge told Good Morning Britain on Monday that the test was just that - a test, which was intended to iron out any issues.

“You can only do so much in the laboratory to see if something is going to work," he said. “This is why we test fire alarms in buildings when there are no fires.

“It is not unusual that a test of this type did not work perfectly. That is what you expect. I don’t think anyone in the mobile phone industry would be surprised that it wasn’t perfect.”