BBC supernova!
A supernova a short lived  stellar explosion marking the end of the life of a star. Over the next few weeks BBC local radio will undergoing their supernova equivalent. Before a star explodes into a supernova it may be difficult to see. Right now BBC local radio stations are difficult to 100% identify at night because they carry nationally syndicated programming with no local content. So sending a recording of networked programming to get a QSL card is less than convincing.
But in a few weeks time many stations will switch over to a brief looped recording telling listeners that the MW service about to close down. These looped messages are unique, easy to hear, repeat every few minutes 24 hours a day and are 100% convincing evidence that you heard a particular station. The audio can’t even be recorded from a parallel frequency or off the internet. The only place you’ll hear these message is on MW.
This brief period of super DX visibility will be followed by total extinction as the BBC MW  local radio network collapses and switches off the MW transmitters for good. This super nova experience is your last, but best, chance to hear many BBC local radio stations and to try to get a QSL.
Good star spotting
73 Steve Whitt, MWCircle groups.io via Kari Kallio in nordx groups.io (2021-04-24)