This was a short tour with only a few engagements, but the King's first visit to one of his realms mattered, and Australia was a real test of the monarchy overseas.
Even the palace admits no one knew how the King would go down, down under.
It wasn't without its challenges.
Some had questioned whether the King, who is still undergoing regular cancer treatment, would even make the trip.
And the unexpected outburst from senator, Lidia Thorpe, at the King's set-piece speech certainly wasn't part of the script.
The palace was rattled by the press reaction.
But overall, the Aussies welcomed their King.
Even the Prime Minister Anthony Albanese, a committed republican, has ditched his plan for a vote to remove the King as head of state.
We were though reminded in Sydney that this trip has been reworked for the King's health.
He visited a cancer research centre and met two of Australia's leading cancer doctors.
His own treatment has been put on hold so he could come on the tour. His aides say not coming was never going to be an option.
And they wanted every moment to count.
We're told 9,000 people made the journey to the iconic Sydney Opera House.
And with very few walkabouts planned, this was always going to be a sell-out moment. A showstopper backdrop to the end of their four-day visit.
More on the royal trip:
Alpaca sneezes on King Charles
King meets indigenous elders
Where is King Charles head of state outside the UK?
After the protestor in Canberra, a visit to an indigenous centre in Sydney was far less confrontational.
With a welcome from elders and a private audience with the King.
The community leaders don't agree with how Ms Thorpe protested, but they do share some of her concerns.
Conversations here about colonial history are difficult, but important. And indigenous rights are a fractious cultural fault line that continues to divide Australia.
(c) Sky News 2024: No one knew how the King's trip to Australia would go down - and it wasn't without its challenge
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