It will be the moment when millions of mobile phones will vibrate and ring at the very same time.
At about 3pm next Sunday, an official 'Emergency Alert' will be sent to all 4G and 5G-enabled phones and tablets.
The phones will vibrate and emit a siren-like tone for ten seconds.
But happily, there will also be a message making clear that it is only a drill albeit one of the largest public safety exercises of its kind ever staged in the UK.
The Sunday afternoon timing has chosen by government emergency planners to minimise disruption to work and school routines.
