If you're in the UK it's nearly time for that emergency phone alert test at 3pm, therefore switch your phone off or hide it in a bag/pocket/under a cushion if you don't want to be startled. Pretend you're in an episode of Doctor Who when it happens...
Switched phone off just before 3pm and was greeted by this message and emergency alert tone when switched on again. The tone was silenced when OK was clicked but the message remained. There's a flashing red triangle icon (with an exclamation mark inside) that wasn't recorded by this screenshot.
@htw Apparently the message continued to be broadcast for twenty minutes. I received mine early at 14:59:14 (EE Network, Manchester).
@nowster Now wondering whether I would have still got the message if I had left my phone switched off for longer. Apparently 4G phones (plus 5G I assume) only got the message.