Operation Forth Bridge
Just as there is a plan in place for precisely what will happen upon the death of Her Majesty, Queen Elizabeth II (Operation London Bridge), Operation Forth Bridge dictates what will happen when the Queen’s husband, Philip, Duke of Edinburgh, passes. The Duke has been closely involved with the details of the Operation Forth Bridge, just as the Queen has been with Operation London Bridge. The name refers to a suspension bridge linking Edinburgh to Perth; the Queen and the Duke attended the dedication ceremony for the bridge in 1964.
We might hear of it before it happens
Customarily, the public is forewarned that a royal is on his or her deathbed via Palace bulletin, as was the case with Queen Victoria and George V, reports The Guardian.
But nothing really happens without a Royal Command
At that time, whoever is the Lord Chamberlain (the Head of the Queen’s household; currently, it is The Earl Peel) will consult with the Prime Minister (currently, Boris Johnson) and then seek the Queen’s specific commands regarding the death announcement and the funeral. No other action is taken until the death is formally announced by Buckingham Palace. If the Queen predeceases her husband, then these commands will be made by the reigning sovereign (most likely Prince Charles).