In the days before her death at the age of 96, Queen Elizabeth II approved laws and ministerial appointments, wrote a message of condolence to Canada following a mass stabbing, and appointed Liz Truss as the UK's new Prime Minister.
Boris Johnson told the BBC, she was "bright and focused", when he gave his resignation.
University of Otago's Professor Yoram Barak is a world-leading expert in neurodegenerative diseases, authoring and co-authoring 150 peer-reviewed articles on psychiatry.
READ MORE: Queen Elizabeth II's state funeral: What you need to know
He says Her Majesty was an "optimal" example of how to remain sharp in old age.
"The fits with our research... the term is an escaper. She escaped every major physical and mental illness."
Some reasons are obvious, he says. An impeccable diet and a devoted royal physician reduced the risk of high blood pressure and diabetes, drivers of dementia.
But her schedule also provides some clues.
Elizabeth's daily routine, over 70 years, changed little. She devoted a good chunk of her day to her duties as sovereign, whether approving laws, ministerial appointments or conversing with global heads of state.
These tasks, says Barak, were ideal exercises for the mind, work that was complex, meaningful, and every day, different.
"Her constant engagement in very challenging social situations, meeting this or that diplomat, making those decisions, are extremely important because she needed to synthesize novel information in ways challenging to the human brain."
"And people with a very clear purpose in life, are very much protected, from dementia or memory issues."
But also important, says Barak, was the time Britain's monarch made for her own leisure, hours spent reading, riding, and listening to the radio. Elizabeth was also famously protective of an hour-long walk in the palace gardens every afternoon.
"A very physically active woman. .. and privileged to be able to walk in nature."
"Brain imaging... shows a walk in nature will very, very positively impact your brain health when the same walk in an urban setting does not."
One constant
However, these pieces of the puzzle, pale in comparison to her one constant - Prince Philip.
"Research coming out of Harvard University, the world's longest study, shows in black and white, very clearly ... that a supportive partnership throughout life is the best predictor of cognitive health."
Queen Elizabeth II, who Philip called Lilibet in private, has been recorded as calling him “her rock” in a rare display of public affection.
The Prince Consort, in turn, once told an old navy friend Michael Parker that "his job - first, second and last - was never to let her down.”
And when he died in April 2021, at the age of 99, it was the moniker, Lilibet, that Queen Elizabeth used to sign the farewell note placed on his coffin, marking the end of their 73-year romance.
Sadly, says Barak, it is possible the loss of Philip, a man she called her "constant strength and guide" may have played a part in her death, 516 days later after his passing.
"Loneliness is a very painful, physically and mentally a very negative force in our lives."
The loss of a loving companion, he says, greatly increases the chance of cognitive impairment, suicide and physical illness.
And although the Queen was surrounded by loyal aides. Philip was the only person who "simply treated her as another human being," according to her former private secretary Lord Charteris.
"Loneliness and social isolation, are two completely different things, and social engagement does not necessarily serve as an antidote."
"Given what we know about that partnership, I think that toxic force of loneliness would have hit her in a very significant way."
Lessons for NZ
And lessons from the Queen's life and death, he says, cast a dark shadow over the state of New Zealand's older population.
A paper Barak co-authored in 2020 showed Aotearoa's elderly were dying at higher rates, compared to Australia, despite similar lifestyles.
"We came out tremendously badly on nearly every index."
Dr Ngaire Kerse is the Principal Investigator at Auckland University's Brain Research New Zealand, and the Joyce Cook Chair in Ageing Well.
The shocking statistics are partly due to our medical system, and how it cares for the old.
But this paints only part of the picture.
New Zealand, she says "is also growing lonely, older people."
The signs, she says, are obvious when you know what to look for.
"Public transport is not conducive to older people... once you lose the ability to drive it can be really, really difficult to maintain relationships."
"We have a pension, which is inadequate, which you can't live on unless you own a house, and we've got a terrible housing situation.
These are just some examples, she says, of the barriers preventing full participation in life for older people "which would go a long way to tackling loneliness."
"The irony is, we adored the Queen, but we don't value our old people."
We’ll have full coverage of Queen Elizabeth II's State Funeral on Monday in a 1News Special from 7.30 pm on TVNZ 1, and on 1News.co.nz.
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