She, like billions of others, is sheltering at home, though in her case that's Windsor Castle with more than 1000 rooms.
Little is known about how she celebrated the actual day. A palace spokesperson said last week: "Her Majesty's birthday will not be marked in a special way – and calls, video calls, with family will be private and kept so."
However, it would seem Harry and Meghan, the Duke and Duchess of Sussex, might have missed this particular royal missive, given reports they shared details of the call with select group of media.
BITTER BATTLE
On Monday this week, the couple sent a letter to four UK newspapers announcing they would offer them "zero co-operation" in the future, an escalation in the Sussexes' battle with some sections of the UK's tabloid press.
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It was an unprecedented move and the Times reports that while the Queen was made aware in "the broadest terms" of their plans beforehand, Prince Charles was not told.
The situation bears a resemblance to early January when the couple announced they were quitting as frontline working members of the royal family, allegedly leaving the royal family "blindsided".
The picture that has emerged in recent months is of Harry and Meghan charting their own course with the media, essentially operating in a silo.
For example, in March when they briefly returned to the UK from Canada for their farewell tour.
To mark International Women's Day, Camilla Duchess of Cornwall was giving a significant speech about domestic violence.
According to The Mirror (one of the papers now blocked by the Sussexes) there was an understanding to not overshadow the moment.
According to the March report, Camilla was reportedly left "very upset" when Meghan allegedly asked that photos of her visiting the National Theatre be released on the same day.
Today, the Sussexes are thousands of kilometres away, starting their new life in Los Angeles, but their combative approach to the press still has the potential to cause headaches behind Palace gates.
The first hearing in the matter of Meghan vs Associated Newspapers, the parent company of the Mail on Sunday, has started. Court documents released prior revealed the Duchess was prepared to lay open details about royal funding to dispute a claim made by the Mail.
The Telegraph reports: "If the discussion about funding goes ahead, it is understood it could go into details of money relating to Frogmore Cottage, wedding costs, security, and funding through the Sovereign Grant or the Duchy of Cornwall".
This could open a very uncomfortable Pandora's box for the Queen, the extent of whose personal wealth remains a mystery. (Forbes has pegged a figure of about $960 million.)
There has long been a significant amount of public sensitivity about how much the monarchy costs British taxpayers, either in terms of the security bill or how much of the revenue from the Crown Estates goes back into The Firm's pockets (the Sovereign Grant) rather than into the state's coffers.
The royal family is pretty cagey about just how much dosh (and paintings and diamonds and who knows what else) they have squirrelled away.
Getting into the nitty gritty of how the Windsors spend some of their money could be embarrassing for the sheer number of noughts at the best of times.
However, given the world is teetering on the edge of economic collapse, this sort of disclosure could be disastrous PR-wise.
With the Queen, Charles, William and Kate all earning gold stars and plaudits for their Covid-19 response, a reminder of the sheer amount of money it takes to keep the monarchy machine going could seriously dent their shiny public images right now.
Since day one, the Sussexes have charted their own course, and their current legal action and clash with Fleet Street fit perfectly with their renegade MO.
But that is probably cold comfort for the Palace's PR apparatchiks because incidents such as this week's call being made public seem to suggest that the Sussexes are embracing a go-it-alone, DIY approach, putting them at odds with more established Palace practices.
In late March it was confirmed the Trooping the Colour would not go ahead "in its traditional form" which, given the Windsors' new-found penchant for Zoom, could mean the first remote military parade could be in the offing.
It will be fascinating to see who logs in for that video call – and how it is made public.
