Queen Elizabeth II opened the 2015 Commonwealth summit on Friday with a colourful ceremony attended by world leaders gathered for pressing talks on climate change.
The monarch, dressed in an aqua blue coat with pink flowers adorning her trademark hat, was serenaded by a harp as she arrived to a red-carpet welcome at a huge sandstone conference centre on the seafront in the Maltese capital Valletta.
As the clock ticks to a UN climate conference in Paris starting Monday, leaders at the summit including France's Francois Hollande, Britain's David Cameron and the UN's Ban Ki-moon will try to open the door to a landmark accord for limiting greenhouse gases.
"At this meeting, the Commonwealth will be charged with demonstrating leadership, often in practical ways, on an agenda of global issues," Queen Elizabeth said in her opening address on the Mediterranean island.
"I wish you every success in this endeavour." She spoke of the Commonwealth's potential to tackle climate change - giving as an example the Commonwealth Canopy initiative to protect the world's forests - and stressed the importance of getting young people involved in the fight to slow global warming.
In a nod to the young, children took to the stage for the opening ceremony dressed up as animals and characters from each of the 53 Commonwealth countries.
Born out of the British empire, the Commonwealth of Nations brings together around a quarter of the world's countries and a third of its population. The 24th biennial summit is due to focus on the issues of extremism and migration as well as the environment.
Among the prime ministers who took their seats in the ceremony as their flags flashed across giant screens overhead, were Canada's new leader, Justin Trudeau, Pakistan's Nawaz Sharif and Pakalitha Mosisili from Lesotho.
The hope is that by finding common ground in Malta - among countries that differ enormously in terms of culture, size, GDP and diplomatic muscle - the COP21 talks in Paris can break through a logjam of highly contentious issues.
Potential stumbling blocks in Paris abound, ranging from financing for climate-vulnerable countries to scrutiny of commitments to curb greenhouse gases and even the legal status of the planned accord.
The last attempt to get a global climate deal - at the ill-tempered 2009 Copenhagen summit - foundered upon divisions between rich and poor nations.
Hollande, as president of the COP21 conference's host country, is expected to make an impassioned plea at the Commonwealth summit later Friday, before diplomatic toils continue on the sidelines of a banquet hosted by Queen Elizabeth.
While France is not formally taking part in the Valletta talks, Hollande is seeking to send out a message "on the vision of the French presidency for an ambitious, equitable, durable and dynamic (climate) deal", the presidency said.
The objective in Paris is to forge a post-2020 deal that will prevent global warming from breaching two degrees Celsius (3.6 degrees Fahrenheit) above pre-industrial levels.
"We do not have the right to test to destruction the planet's tolerance to our indiscretions. We do have a responsibility to act now," Queen Elizabeth's eldest son Prince Charles said in a speech Thursday.
Countries most at risk - including low-lying small island states and poor nations in Africa, many of them Commonwealth members - have called for capping warming to 1.5 C, saying anything less would result in catastrophic impacts.
The Commonwealth's Business Forum warned it was not just vulnerable nations that would pay the price of inaction, and companies globally would have to react to survive.
An accord would mean little if the private sector could not be persuaded to get behind the climate change fight, it said.
It is understood that Queen Elizabeth, head of the Commonwealth since 1952, will not undertake long-haul travel for future summits.
"I feel enormously proud of what the Commonwealth has achieved, and all of it within my lifetime," she said, citing "a vast expansion of human freedom" with "millions of people sprung from the trap of poverty".