When she pledged herself, aged just 21, to a life of service to the people of Britain and the Commonwealth, few could have predicted just how long her commitment would endure.
Princess Elizabeth went on to make history as Queen Elizabeth II, the country's longest-reigning monarch and the first to celebrate a Platinum Jubilee.
Remarkably, 75 years after her solemn vow to serve and despite failing health, she renewed her pledge, while also setting out her hopes for a future beyond her reign under King Charles.
The Queen at her Coronation in 1953
The young Princess Elizabeth was not born to be Queen, but became heir presumptive aged ten, when her uncle, King Edward VIII, abdicated to marry the American divorcee Wallis Simpson.
With her destiny as a future monarch determined, she nevertheless found herself propelled into the role earlier than expected following the sudden death of her father King George VI.
When she came to the throne in 1952, as a 25-year-old mother of two very young children, few people had a television, barely one in five adults owned a car and the Internet did not exist.
The second Elizabethan era began in post-war Britain and spanned a period covering the troubles in Northern Ireland, the era of the three-day week in the early 1970s, the Falklands War, the miners' strike and the poll tax riots.
The Queen pictured during her Platinum Jubilee celebrations in June
It saw the removal of most hereditary peerages, the legalisation of same-sex marriage, and the dawn of a new Millennium and has finally ended in our modern age of virtual currencies, driverless cars and the Covid-19 pandemic.
As the world encountered vast social, political, cultural and technological changes the Queen was quick to embrace the new, whether using social media or holding virtual audiences in her final years.
She also became the most travelled monarch in history, visiting more than 120 countries and famously saying, "I have to be seen to be believed".
With her "strength and stay" Prince Philip at her side, she modernised the monarchy to adapt to changing times, but her devotion to her duties remained unwavering.
The Queen pictured with her 15th Prime Minister Liz Truss
She continued to work almost every day into her late 90s, attending to papers in her famous red despatch box even while unable to carry out engagements in person.
And despite difficult personal times – the divorces of three of her children, the legal woes of her son Prince Andrew and more recently the loss of her beloved husband – she never deviated from her duty.
Indeed, her steadfast presence and her winning blend of the traditional and modern made her a beacon of stability, providing reassurance in an ever-changing world.
On the global stage and especially throughout the Commonwealth, her ability to convene the great and the good was unmatched, all while remaining politically neutral.
And at times of crisis she was able to both comfort and unite people with a well-timed public address or gesture.
Even her unmistakeable image – the immaculately curled hair, white gloves and trusty black Launer handbag – echoed the stability and dependability associated with her reign and made her the most recognisable woman in the world.
This new chapter in our history will feel strange to so many of us as her familiar silhouette is replaced on banknotes, coins and stamps and her presence – so deeply ingrained in our national psyche – is no longer felt.
But, while her incredible reign is unlikely to be matched in, she leaves an amazing example of service, duty and selflessness for those who follow in her footsteps.
Now is a time for mourning – for Her Majesty, her family and for the nation. But then we must look to the future and the generations she has inspired.
As she said in her address to the Cop26 summit last year: "We none of us will live forever. But we are doing this not for ourselves, but for our children and our children's children and those who will follow in their footsteps."
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