Hello, Rosalind!
The code words for a Royal death has been in place for many years.
The late King George the Sixth's code was Hyde Park Corner.
I would imagine in years gone by, long before we had instant communication, or, possibly in times of war, it was thought to be necessary.
It is not anything I have explored, just a bit of info I happened across.
There is a lot of protocol etc with Royalty, so the "codes" may, or may not, have something to do with that.
For instance, every major newspaper will have obituaries written, right now, for the death of any major Royal.
A simple code will get get the process into operation.
That is only what I think, and others will have different opinions.