It was always a question of when, not if, the queen would speak.
Not because there is a rule for these broadcasts. There were four, in very different circumstances.
The start of the land war in Iraq in 1991; the death of Diana, Princess of Wales; the death of the queen’s mother; and a short message of thanks after the Queen’s Diamond Jubilee celebration.
They are not requested by the government, the Palace discreetly corrects those who suggest it. They are carried out after agreement between Downing Street and Buckingham Palace.
The royal family was discreet in this period of national crisis, the palace officials are aware of this. This was partly necessary – the Queen and Prince Charles are both over 70 years old and had to follow government advice to isolate themselves.
In a more “normal” crisis, William and Kate could have been more visible. But the government’s request that people avoid everything except essential travel has meant that their appearance in hospitals or among other key workers would have sent very confusing signals
Similarly, a program by the Queen during the first weeks of the pandemic could have hampered urgent government messages.
There may not be a rule for the timing of these shows, but there is a thread that links them.
The Queen and the royal family have many roles: constitutional, ritual, fun stuff like Garden Parties, visits to towns and villages, support for charitable causes.
But above all, there is an idea, that of unifying. To provide a rallying point of some form in a nation of surprising variety.
When the nation is divided, the queen does not speak, it is for the government and the opposition to fight.
No program was broadcast during the Iraq war in 2003, nor during the invasion of Egypt in the 1956 Suez Crisis. Both involved the armed forces serving on behalf of the Queen. But the two have seen bitter divisions in the country.
Nor did she speak of power cuts and blackouts and industrial action in the country in the 1970s.
Calls to unity at these times could easily be interpreted as supporting one party or another.
But the situation today is very different.
The Queen does not suffer from the same challenges as those locked up in small apartments and houses, those unemployed or facing unemployment. She’s in Windsor where there is more than enough space to relax.
But her son, Prince Charles, was infected with Covid-19.
And through the state newspapers she receives daily, newspapers and broadcasting, she is as aware as anyone in this country of the immense challenges that so many people face.
Don’t expect her to be the national nanny. Hand washing and home support requests will be left to the government.
Instead, it will project the calm determination which it believes is part of the national character of Great Britain. As she did when she spoke after her mother died, she is also likely to thank.
And as the sovereign of a nation that enjoys its history, a return to previous challenges is to be expected.
But this message will mainly focus on unity. About meeting in a period of national struggle.
Unity is the raison d’être of these shows and the raison d’être of the royal family. And the unit will be the Sunday message.