The sprightly 92-year-old was touring a care centre in Norfolk when he spotted a little girl sitting on a beach ball. He quipped: "Do you get bonus points if you knock her off?"
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The joke was taken in good spirits by the little girl's 93-year-old great-grandmother Florence Crisp. Meanwhile twenty-two-month-old Ella was oblivious to the mirth she had caused.
Philip made the comment as he observed an activity class during which residents of the centre kicked beach balls around the room.
"This is dangerous", he joked – before turning to residential block manager Elaine Stamp, asking: "Health and safety people?" She replied, jokingly: "Health and safety goes out the window."
During his tour of the £4 million St Michael's Care Complex in the market town of Aylsham – where many of the residents are younger than him – the Prince was presented with a gift for his great-grandson Prince George.
Residents had made a quilt for the baby printed with and sayings and wisdom to guide him through his life. Some of the gems included "keep your nose clean" and "find your own way in life".
Philip and the monarch are looking forward to the royal baby's 23 October christening, which will take place at The Chapel Royal, St James’s Palace – where Princess Beatrice was also baptised.