They say it could be the sound that saves your life.

For the first time ever in the UK, at 3pm this Sunday, the government will be trialling their new mobile emergency alert system.

Phones right across the country will sound and vibrate all at once.

So, why now has the government given this the get go? And what has been the reaction so far?

ITV News Political Correspondent Harry Horton tells ITV News Presenter Tom Bradby what you need to know...