A former officer in the Household Cavalry, Mr Van Cutsem had been close to Prince Charles since their days together at Cambridge University in the Sixties.
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The friends' shared interests included rural life, field sports and shooting, and the pair regularly holidayed together.
His son Edward was a pageboy at Charles' 1981 wedding to Lady Diana Spencer. And his granddaughter Grace was the much talked about flower girl at Prince William and Kate Middleton's wedding.
The cute five-year-old daughter of Hugh and Rose van Cutsem proved a real talking point when she put her hands over her ears on the balcony of Buckingham Palace when the newlywed royals shared a kiss.
William and Kate's inner circle of friends includes Mr Van Cutsem's four sons Edward, 39, 36-year-old Nicholas and William, 33. It's likely one of them may be asked to be godfather to Prince George.
Hugh and his wife Emilie lived for a time at Amner Hall, on the Queen's Sandringham Estate, during their 42-year marriage. The residence is now tipped to be the country home of William and Kate.