The Prince and his wife, Camilla, the Duchess of Cornwall, were the last mourners to arrive at Brentwood Cathedral in Essex to honour the life of the 72-year-old, who passed away peacefully at home on 2 September.
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His sons, Prince William and Prince Harry, also attended to pay their respects, discreetly arriving together at just after 10.30am.
The turnout of leading royals was hardly surprising given the van Cutsems' close ties to Charles and his sons.
Despite their low-profile, Hugh and his Dutch wife Emilie have proved to be hugely important and instrumental in the lives of Charles and his boys.
Hugh, a former officer in the Household Cavalry, first became close to Charles during their time together at Cambridge University in the Sixties.
Their friendship endured, and when Charles married Lady Diana Spencer in 1981, the van Cutsem's eight-year-old son Edward, who is also Charles' godson, was one of their two page boys.
As Charles' marriage to Diana broke down, the van Cutsems became hugely important to his sons William and Harry.
They spent a great deal of time with the family during that time, and became good friends with the couple's four sons, William, Edward, Hugh and Nicholas — many people felt that it was in large part thanks to the van Cutsems that the two Princes were able to enjoy something approaching a normal childhood.
(From left to right) Hugh and Rose van Cutsem and Nicholas and Alice van Cutsem
The next generation have remained close. In a move that mirrored his parents' own marriage 30 years previously, William and Kate asked Grace van Cutsem, the five-year-old daughter of Hugh and Rose van Cutsem, to be a flower girl on their wedding day.
It is also highly likely that the royal couple will ask either Hugh, 39, Edward, 40, Nicholas, 36, or William, 33, to be a godfather to their son, Prince George.
During their 42-year marriage, Hugh and his wife Emilie were Sandringham neighbours of the Queen as the leaseholders of Anmer Hall; the 10-bedroom property that has been earmarked as a country retreat with William, Kate and Prince George.
In 2004, the Queen and Prince Philip were among the guests attending Edward van Cutsem's wedding to Lady Tamara Grosvenor, the Duke of Westminster's daughter.
After their lease expired, the van Cutsems moved into a country house on their own estate at Hilborough, near Swaffham in Norfolk.