King Charles surprised members of the public enjoying a stroll in central London on Sunday when he arrived at Kensington Palace via helicopter.
The monarch was spotted touching down inside the palace grounds, where he was immediately greeted by Princess Eugenie's husband Jack Brooksbank and his two sons August and Ernest.
After Charles, dressed in a grey suit, departed via car, hands-on dad Jack escorted four excited children, including his two sons, to the red helicopter.
The royal kids spent around ten minutes observing the impressive chopper, just out of view from the crowds forming outside.
King Charles surprised members of the public enjoying a stroll in central London on Sunday when he arrived at Kensington Palace via helicopter
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After their brief tour, Jack shared a sweet moment with his sons, ruffling their hair and chatting close to their ears as they walked back to Kensington Palace.
Captivated by the King's mode of transportation, the young royals continued "watching from the house" as it took off again.
Jack and Eugenie are enjoying family time in the UK, where they stay at their private residence, Ivy Cottage on the Kensington Palace grounds.
The couple keep their three-bedroom grace-and-favour property largely away from the spotlight.
August Brooksbank is the oldest child of Princess Eugenie and Jack Brooksbank
Instagram / Princess EugenieFans have had rare glimpses inside from Eugenie's family photos and Prince Harry's video with Ed Sheeran.
The family also spend considerable time at their Portuguese home in Comporta, where Jack manages a 300-home development.
King Charles' fleeting appearance comes just one week after his "brief" hospital visit due to side effects from his ongoing cancer treatment on Thursday 27 March.
He momentarily stepped back from royal duties and postponed some engagements in Birmingham after requiring "a short period of observation in hospital," according to Buckingham Palace.
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Princess Eugenie and Jack Brooksbank have two children
Princess Eugenie / InstagramIt was thought that he travelled to Highgrove Estate in Gloucestershire - one of his most cherished properties.
Charles' break was short-lived, as he quickly returned to royal engagements, including hosting a community music reception at Windsor Castle.
The 76-year-old monarch and Queen Camilla will leave the UK in the next 24 hours to begin their four-day trip to Italy.
The visit will include several formal engagements across Italy, demonstrating the King's improving health and ability to resume royal responsibilities.