It was 1947 on the occasion of her 21st birthday and with the palace already looking to the future she gave a speech to assure her people that hinted that should there be any change of guard at the royal household, it would be the last for a generation.

“I can make my solemn act of dedication with a whole Empire listening,” she said during a visit to South Africa with her parents, on her first overseas trip.

“I should like to make that dedication now. It is very simple. I declare before you all that my whole life whether it be long or short shall be devoted to your service and the service of our great imperial family to which we all belong.”

She concluded the address with: “God help me to make good my vow, and God bless all of you who are willing to share in it.”

She did take the throne, an accidental monarch in many respects, but royal insiders today will tell you it was this sentiment that she has carried with her whole life from the moment she wore the crown of St Edward and one she has referenced several times both in public and privately during her more than 60 years on the throne.

“Bookmakers and others are always suggesting her majesty is set to abdicate and hand over the throne but you only have to hear that speech to know this will never happen,” a royal court insider said this week.

The Queen’s life in pictures

On September 9, Queen Elizabeth II will pass the record set by her great-great-grandmother Queen Victoria as Britain’s longest serving monarch.

Buckingham Palace has calculated that Queen Victoria reigned for 23,226 days, 16 hours and 23 minutes, taking into account 63 years, 15 leap days and the precise timings of her accession and death.

Queen Victoria had taken the throne when she was 18 and stayed there until she died age 81 in 1901.

It may be a European fashion of sorts to abdicate — reigning monarchs in Netherlands and Spain did just that recently — but not the 89-year-old Queen Elizabeth.

“Life means life … and in keeping with her style she will pass the milestone of her reign with the attitude of business-as-usual, carrying out an official engagement in Scotland no fuss and coincidentally we know from the records Queen Victoria also took the same attitude when she became the longest serving monarch,” the royal court insider said.

“She has never wavered from that position, that pledge she has made to serve her people to the best of her abilities, of course for as long as she is able.

“She considered it a job for life as long as her age and health allow it.”

The Queen and Duke of Edinburgh will be on a steam train in Scotland, opening a new route from Edinburgh to the Scottish border on the day of her milestone.

When she ascended to the throne on February 6, 1952 — following the death of King George VI after he passed away in his sleep after a 16-year reign — and again on June 2 the following year during her formal coronation, she made an oath.

It was to serve her people as Queen of the 16 of the 53 member states of the Commonwealth, as head of the Commonwealth and Supreme Governor of the Church of England.

It was in that first ever televised coronation, and before 8000 invited guests and millions more worldwide she took the oath of reign and was handed the four symbols of authority — the orb, the sceptre, the rod of mercy and the royal ring of sapphire and rubies. She also swore on the bible before the crown was placed on her head.

Her ascension to the throne gave Britain a little colour in an otherwise dark period of post war Britain.

She was young and beautiful and was married to a dashing officer whom she met when she was 13 and would marry eight years later, six months after she made her 21st birthday pledge to the realm.

She was never supposed to be Queen with her uncle Edward the Prince of Wales expected to run the realm and then have heirs of his own. He did take the crown when King George V died but then in that same year, 1936, he abdicated to marry divorcee Wallis Simpson and Princess Elizabeth’s father become king and she the “heir presumptive”. Again, few expected her to become Queen as her parents could still have a son to leap frog her position.

At the outset of the war, though she was only 13, she met her future husband Philip when her father visited the Royal Navy College in Dartmouth. They would go on to exchange letters throughout the war.

During those difficult years it was suggested Elizabeth and her younger sister Margaret be moved to Canada for safety but instead midway through the conflict she undertook public duties in the Auxiliary Territorial Service where she trained as a driver and mechanic.

Her engagement to Philip was announced in July 1947 and they were married in November of that year.

During her diamond jubilee in 2012 the Queen credited Prince Philip as her rock that had allowed her to continue in her role as the head of state for so long. He was, she said, “a constant strength and guide”. Years earlier during her Golden wedding anniversary in 1977 she said Britain and many other countries including Australia “owe him a debt greater than he would ever claim or we shall ever know”.

She has experienced a lot of personal highs and lows during her long reign and has overseen many changes but the affection her people have had for her has never changed.

She has cited one of her highs as being when she became the first reigning monarch to ever visit Australia in 1954 during which it was said the crowds were so huge it was estimated three quarters of the population came out to see her.

Her low moments would be the breakdown of the marriages of her children in 1992, the Duke of York and Princess Royal to their respective partners and a tell-all book by Lady Diana after her split from Prince Charles, after which the Queen made her infamous ‘annus horribilis’ speech. Her other low moment was the 1997 death of Diana for which she was initially demonised by the British press for her apparent detached reaction to the passing. Other low times came with the death of her mother and sister in 2002.

Then there have been the various controversies and public embarrassments over the years that have mired her children, particularly Prince Charles and Prince Andrew. But throughout her reign — which has encompassed the Cold War, the Suez crisis, Cuban missile crisis, the Falklands War, the Gulf wars, terrorism at home and abroad, the reign of 11 British prime ministers and many social changes her public popularity has wavered little.

In 2012, at the age of 86, she began to hand more formal duties over to the heir apparent Prince Charles, a kind of job share scheme, but no-one believed she would ever step down.

“This is not going to be a sudden shift,” a royal aide said at the time. “It is a gradual process which will be borne out over the next few years. It’s a gentle succession.”

Even when the following year Queen Beatrix of the Netherlands stepped down to allow her son Willem to take the reins there was much speculation if Elizabeth would do the same. Then in 2014 King Juan Carlos of Spain handed the crown to his son and questions were raised.

But she has remained steadfast in her resolve, true to her word in 1947 that she was at the service of the people for as long as she was able to physically and mentally do so or was to live.