Mobile phone emergency alert test.

www.bbc.co.uk/news/uk-64999417
When I read about this on my local Nextdoor site I thought it must be a scam. However, it seems it is true. On April 23rd every smart phone will receive a test siren alert, whether switched on or not, which must be acknowledged before the phone can be used.
Apologies if you already know about it, but it was a first for me.