King Charles arrived at Kensington Palace on Sunday afternoon via helicopter - much to the delight of Princess Eugenie and Jack Brooksbank's two sons, August, three, and Ernest, one.
The monarch was spotted touching down inside the grounds of the palace, where he was immediately greeted by Jack and his boys.
According to reports in Hello! Magazine, the public were also delighted when Charles appeared to disembark, wearing a grey suit, and he shortly departed via car.
Afterwards, Jack escorted excited children, including his two sons, to the red helicopter, and the kids spent time observing and looking at the chopper - just out of view of forming crowds.
A source told HELLO! that "lots of onlookers" watched August and Ernest's exclusive up-close look at the royal helicopter.
Captivated by the King's mode of transportation, the young royals continued "watching from the house" as it took off again.
When Jack and Eugenie are in the UK, they stay at their home at Ivy Cottage on the grounds of Kensington Palace. Thanks to Jack's latest business venture, the family also own a sun-soaked home in sunny Portugal.
The family have a home near the CostaTerra Golf and Ocean Club resort as Jack is now working with property tycoon Mike Meldman, who is managing a 300-home development.
The club is dubbed the "Hamptons of Western Europe" - and is certainly fit for royalty, boasting luxury amenities such as an 18-hole golf course, spa and equestrian centre.
Charles's fleeting appearance comes just one week after his brief hospital visit due to side effects from his ongoing cancer treatment on March 27.
The King momentarily stepped back from the royal spotlight and postponed engagements in Birmingham after he required "a short period of observation in hospital," according to Buckingham Palace.
It was thought that he travelled to his royal residence, Highgrove Estate in Gloucestershire - his property that's situated on 900 acres of gardens.
Charles and Camilla are set to travel to Italy together as they begin their four-day tour starting from tomorrow.
