On the 75th anniversary of the end of World War II in Europe, Queen Elizabeth II made a special address to the nation. Throughout her reign, we learnt to look out for subtle messages during such broadcasts, be it a framed photo on her desk or even the brooches she pinned to her dress.

This particular broadcast carried two significant messages on her desk: a framed photograph of her father, King George VI in wartime uniform and a khaki cap with a badge. The cap belonged to Subaltern Windsor of the Auxiliary Territorial Service. The young Elizabeth had begged her father to let her join the war effort and she wanted to do it in uniform. Her cap took pride of place on the day of the broadcast as it was a simple reminder of what mattered most to her: service.

The dedication to service was the golden thread that ran throughout her reign. As I was watching the rolling news following Elizabeth II’s death, a quote from Twelfth Night kept popping in my head: “Some are born great, some achieve greatness, others have greatness thrust upon them.” Elizabeth was not born to become queen, so she was not technically born to greatness. It was thrust upon her, the job, not greatness. She then strove to achieve greatness.

But how can we measure Elizabeth’s greatness? Her longevity? It’s an accident of nature, just like her being born in the Royal Family is an accident of birth. Always modest and respectful of her place in history, she dismissed her surpassing Queen Victoria as Britain’s longest-serving monarch with characteristic self-effacement: “Inevitably a long life can pass by many milestones. My own is no exception.”

So how does one assess Elizabeth’s reign? Victories on the battlefield? History books are bursting with stories of great monarchs leading their country into battle but Elizabeth was a constitutional monarch as she reminded her subjects in her first televised Christmas broadcast in 1957: “I cannot lead you into battle...but I can do something else, I can give you my heart and my devotion.”

Devotion to service. That is the key to unlocking her entire reign. On her 21st birthday, in 1947, Elizabeth promised that her life, “whether it be long or short”, would be dedicated to service.

Her strong sense of duty drilled into her by her father was burnished with training.

On the eve of the 40th anniversary on the throne, she said circumspectly: “I have a feeling that in the end, probably, training is the answer to a great many things. You can do a lot if you are properly trained and I hope I have been.”

She was.

In his first address as king, Charles III, her son, eloquently said that her promise with destiny was kept. It was more than a promise, he continued, it was a profound personal commitment which defined her whole life.

Humility is another characteristic that Elizabeth possessed. Her long reign was not without mishaps, mistakes, tragedies and lapses of judgment but she was never afraid to walk back from them. When Diana, Princess of Wales, was killed in Paris, the queen refused to leave Balmoral even as her people clamoured for her to return to London.

You don’t need to be a monarchist to appreciate the virtues Queen Elizabeth II embodied in public life- Alessandra Dee Crespo

Later we learnt that she wanted to stay with the young princes William and Harry, maybe the only time when family came before the Crown and it nearly brought the monarchy to its knees. But she listened to her government as was her duty, returned to London and delivered a heartfelt, brief speech where she spoke of “lessons to be learned”.

The queen was not above learning important lessons. But she did it on her own terms, according to her set of time-honoured values by resolutely maintaining the dignified and crucial distinction between private life and public life, between how one might feel and how one behaves.

She wasn’t above sending herself up, either. In the midst of tradition and duty, the queen still found the time for surprises. Who can forget her skit with James Bond and Paddington Bear? You can never be too grand to produce a marmalade sandwich from your handbag.

If, along the way, she was regarded by some as a symbol of all that was wrong with a class-ridden society, she came to stand for those old-fashioned virtues that are in such short supply in public life these days: restraint in a time of self-importance, and selfless public service in an era of self-worship.

You don’t need to be a monarchist to appreciate the virtues she embodied in public life: self-sacrifice, emotional continence and unwavering duty.

Queen Elizabeth was a study in quiet leadership. “There’s no single formula for success,” as the queen herself told the United Nations in July 2010, “but, over the years, I have observed that some attributes of leadership are universal and are often about finding ways of encouraging people to combine their efforts, their talents, their insights, their enthusiasm and their inspiration to work together.”

Surely, a lesson learnt from her own father, George VI, who, during wartime, by wearing the uniform of service and by refusing to leave his people to face hardship of the Blitz alone, he united his people behind a common cause and inspired them with his example of duty at all costs.

“All had a part to play,” reminisced his daughter about the war during the special broadcast. And she made sure she played her part by keeping the promise she made all those years ago to her dying day.