Australia's staunchly republican prime minister Malcolm Turnbull has welcomed the Prince of Wales to the capital and declared that he will become King of Australia - unless there is a constitutional change.
The two men met on the tarmac at a military base in Canberra, a moment that had been billed as potentially awkward for the heir to the throne given Mr Turnbull's views.
In his book The Reluctant Republican Mr Turnbull levelled personal criticism at both Charles's marriage to Diana, something he described as "a miserable pretence'', and his relationship at the time with Camilla.
Mr Turnbull also wrote about his frustration at Charles giving the longest speech on Australia Day in 1988, the bicentennial year of the nation.
He wrote that the address "was not uttered by an Australian. It was given by an Englishman, Prince Charles'', adding: "Our own national leaders were just warm up acts for Prince Charles.''
He also wrote: "While the Queen still generated enormous affection and respect, it was difficult to believe that Prince Charles could ever be accepted as King."
Asked about that comment today, Mr Turnbull said he had no doubt that Charles would succeed the Queen.
He said: "If Charles becomes king of the United Kingdom - and I have no doubt that he will be - unless our constitution has been changed, he will become the king of Australia."
Asked if he were happy about that, the prime minister replied: "I am a happy person."
Charles and Camilla arrived in the national capital as the nation marked the 40th anniversary of a constitutional crisis that convinced many that Australia should severe its constitutional ties with the British monarchy.
In November 1975, Governor General John Kerr, the Queen's presentative in Australia, dismissed the elected government of prime minister Gough Whitlam.
Today, after Charles and Mr Turnbull had honoured Australia's war dead by laying wreaths during a national Remembrance Day ceremony at the Australian War Memorial, they sat down to talks at Government House.
Charles arrived in the meeting room first and joked with the waiting press about the persistent downpours that had soaked guests during the open-air ceremony, asking if anyone had got wet.
When he was questioned about whether he had got wet, he said "rain's a blessing" then added: "I did a bit - my bottom."
Mr Turnbull soon arrived and the two men were all smiles when they shook hands for the waiting cameramen.
They appeared at ease in each other's company and even shook hands again when asked to by a photographer.
The prince and prime minister were joined by their aides for the meeting that lasted around 30 minutes.
During the day Camilla sampled scrambled eggs infused with truffles and ice cream featuring the same coveted ingredient when she visited a farm that produces the delicacy.
Braving heavy rain Camilla and the Australian prime minister's wife Lucy Turnbull were also treated to a truffle hunting demonstration.
They watched as Samson, a black labrador, weaved around trees until he found a truffle that had been hidden by French Black Truffles farm manager Jayson Mesman,
Damian Brabender, the executive chef of Canberra's Sage Dining Rooms, put on the cookery demonstration for the guests who marvelled as he created ice cream by putting dry ice into a cream, sugar, egg and truffle mixture that produced a mist.
Later Charles and Camilla visited an arboretum dedicated to saving rare and endangered trees.
The 250 hectare site, which opened two years ago, has 44,000 trees from over 100 counties.
The prince, who planted a pin oak tree, told visitors that the day's wet weather was a good sign for the arboretum.
"I am thrilled it's raining," he said "Maybe it will help them grow."
Earlier he toured the National Museum of Australia, which has strong ties with Britain.
The British Museum is sending 150 Aboriginal and Torres Strait Islander objects to Canberra for an exhibition which opens later this month.
The museum is also about to launch a scholarship programme for indigenous communities, in a partnership with The Prince's Charities Australia.