Queen Elizabeth II openly voiced her wish for her son Prince Charles to succeed her as head of the Commonwealth as she opened the group's summit for potentially the final time.
Queen Elizabeth, who turns 92 on Saturday, welcomed leaders from the 53 Commonwealth nations -- mostly former British colonies -- to Buckingham Palace to start two days of talks focused on trade, marine protection and tackling cyber crime.
In her opening speech, Queen Elizabeth spoke of her own "extraordinary journey" since pledging to serve the Commonwealth for life when aged 21.
"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," she said, referring to her eldest son Charles.
Queen Elizabeth has been the Commonwealth's symbolic figurehead since her father king George VI's death in 1952. On Friday's closing day, leaders are expected to decide who should follow her in the non-hereditary role.
Charles, the heir to the thrones of 16 Commonwealth nations, now seems certain to get the nod following Queen Elizabeth's public endorsement -- despite some republican voices angling for change.
Turnbull, Trudeau back Charles
Charles, 69, told Commonwealth leaders the body had been "a fundamental feature of my life for as long as I can remember".
He hoped the 2018 summit would give the group "renewed relevance" to citizens, making it a "cornerstone" for future generations, as it had been for him.
Australian Prime Minister Malcolm Turnbull still supports staying in the Commonwealth under future monarch Prince Charles.
"Australia, as you know, strongly supports the continuation of the king or queen of the United Kingdom as the head of the Commonwealth," Mr Turnbull told reporters in London on Thursday.
"Prince Charles in time will succeed his mother."
While Mr Turnbull once led the campaign for Australia to become a republic, he said there was no inconsistency with wanting a British monarch to run the Commonwealth.
"Most countries in the Commonwealth are in fact republics," he said.
Instead he said there was strong support for the ceremonial role Queen Elizabeth has played as head of the Commonwealth since 1952.
"She's provided that leadership for nearly 70 years, it has been remarkable," he said.
"Spanning so many decades, so many leaders, so many chapters of history.
"The head of the Commonwealth, which is a ceremonial role, a role of honour rather than one of political authority, that role I think should continue, and this is the very widespread view, with the Queen's successor."
Canadian Prime Minister Justin Trudeau said: "I very much agree with the wishes of Her Majesty that the Prince of Wales be the next head of the Commonwealth."
And Maltese PM Joseph Muscat added: "We are certain that when he will be called upon to do so, he will provide a solid and passionate leadership for our Commonwealth."
Queen Elizabeth gave up long-haul travel to attend the biennial Commonwealth summits in 2013 and gatherings look set to be held outside Europe in the near term.
British Prime Minister Theresa May, the summit host, paid tribute to the queen's decades of service.
"You have been the Commonwealth's most steadfast and fervent champion," May said.
Clean oceans plea
Born out of the former British empire, the voluntary association, covering a third of the world's population, is hoping to agree an ocean governance charter, an agenda for trade and investment, and a declaration on tackling cyber crime at the London summit.
Ministers told reporters after Thursday's talks that they expected to conclude bold commitments on jointly combating maritime plastic pollution, in Friday's closed-doors session at Windsor Castle.
Britain announced plans to ban the sale of plastic straws, stirrers and cotton buds in England, as part of the push.
Vanuatu's Foreign Minister Ralph Reganvanau said the Pacific Ocean around his tiny island nation was being choked by plastic produced elsewhere and said global industrial powers were not taking the problem seriously enough.
"Our communities rely on marine resources for basic sustenance, the main source of protein. Everything we're eating has plastic in it," he told AFP.
"No proper studies have been done to say what's the effect on us. Sooner or later it's going to become an issue that we're all very aware of.
"The plastic is everywhere. We need to work together as countries and stop, as much as possible, the plastic getting in the ocean."
Given its highly diverse membership, if agreements can be reached within the Commonwealth, they can likely achieve wider support.
At the last Commonwealth summit in 2015, leaders struck a deal on climate change that paved the way for the global Paris agreement days afterwards.
