THE Queen has urged Commonwealth nations to allow Prince Charles to succeed her as head of the Commonwealth "one day", which will spark a rubber stamp of approval from 53 leaders in London on Friday.
Prime Minister Malcolm Turnbull - sitting next to Canadian PM Justin Trudeau - joined other world leaders who rubbed shoulders with the Royal family during the official opening of the Commonwealth Heads of Government Meeting (CHOGM).
The Queen and Prince Charles officially hosted CHOGM's formal Opening in the Ballroom of Buckingham Palace.
The Queen said she was happy to welcome leaders into her home.
"Here at Buckingham Palace in 1949, my father met the Heads of Government when they ratified the London Declaration, which created the Commonwealth as we know it today - then comprising just eight nations," she said.
"Who then - or in 1952, when I became Head of the Commonwealth - would have guessed that a gathering of its member states would one day number 53, or that it would comprise 2.4 billion people? And we seem to be growing stronger year by year. As another birthday approaches this week, I am reminded of the extraordinary journey we have been on, and how much good has been achieved.
"It is my sincere wish that the Commonwealth will continue to offer stability and continuity for future generations, and will decide that one day. The Prince of Wales should carry on the important work started by my father in 1949. By continuing to treasure and reinvigorate our associations and activities, I believe we will secure a safer, more prosperous and sustainable world for those who follow us: a world where the Commonwealth's generosity of spirit can bring its gentle touch of healing and hope to all."
The 53 Leaders were individually announced as they entered the opulent Ballroom, the largest room in Buckingham Palace.
Before they entered the room, leaders were greeted at the Palace by a Guard of Honour, a Regimental Band, a Corps of Drums and Commonwealth flag bearers.
Wearing a green and white two piece blouse and skirt, and her trademark pearls, The Queen, who turns 92 on Saturday, slowly walked to her seat with Prince Charles and her family.
A pregnant Kate Middleton was not seen during the official event.
Prince Charles, a strong environmentalist who is almost a certainty to replace The Queen as the head of the Commonwealth, spoke about the success of the Commonwealth Games on the Gold Coast.
"Witnessing this great gathering of seventy-one countries and territories and meeting their athletes in the Games Village was, above all, a moving reminder of the strong and affectionate bonds which we all share," he said.
"For my part, the Commonwealth has been a fundamental feature of my life for as long as I can remember, beginning with my first visit to Malta when I was just five years old.
"I pray that this Commonwealth Heads of Government Meeting will not only revitalise the bonds between our countries, but will also give the Commonwealth a renewed relevance to all citizens, finding practical solutions to their problems and giving life to their aspirations.
"By doing so, the Commonwealth can be a cornerstone for the lives of future generations, just as it has been for so many of us."
UK PM Theresa May appeared to take a swipe at US President Donald Trump, saying there needed to be push back against those who put up trade barriers and urged for strong action on climate change.
She also paid tribute to the ageing monarch for her service.
The Ceremony reflected the theme of Towards a Common Future.
The British National Anthem performed by Emeli Sande, a British singer songwriter of Zambian heritage.
A 53 gun salute was fired by King's Troop in Green Park to ceremonially mark the opening of CHOGM, and the 53 current members of the Commonwealth.
After the official opening The Queen and Prince Charles hosted a traditional lunchtime reception for new Heads of Government.
In the evening, The Queen's was preparing to host a dinner at the Palace, which was also attended by The Duke of Cambridge, Prince William; Prince Harry, The Duke of York, Prince Andrew; The Princess Royal, Anne; Sophie The Countess of Wessex; The Duke of Kent, Prince Edward; Prince and Princess Michael of Kent and Princess Alexandra.
The dinner was in the Picture Gallery where The Queen gave another speech.
On Friday, leaders will hold talks at a retreat at Windsor Castle, marking the formal end of CHOGM.
It is expected leaders will rubber stamp Prince Charles replacing as The Queen as the head of the Commonwealth.