Prince Charles will bid farewell to his dear friend and trusted confidant Hugh van Cutsem with Prince William and Prince Harry by his side.
Charles and his two sons will be among the mourners gathered at Brentwood Cathedral in Essex on 11th September, to honour the life of the late conservationist.
Charles' wife, Camilla, Duchess of Cornwall, and Kate Middleton are not expected to attend.
Charles and Hugh, a former officer in the Household Cavalry, had been close since their days together at Cambridge University. Hugh shared the Prince's passions for rural life, field sports and conservation.
He and his wife Emilie van Ufford - married since 1971 - managed to keep such a low profile that their influence on the royal family was often overlooked. But there is little doubt that they were hugely important to not only Charles, but also his sons.
When Charles married Lady Diana Spencer in 1981, the van Cutsem's eight-year-old son Edward, the Prince's godson, was one of their two page boys. Thirty years later, at the wedding of William and Kate, Hugh and Emilie's five-year-old granddaughter Grace was the much-talked about flower girl pictured covering her ears on the balcony of Buckingham Palace.
William and Harry spent a great deal of time with the van Cutsem family as their parents' marriage broke down, and became close 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 brothers were able to enjoy something approaching a normal, carefree childhood.
It is likely that one of the four van Cutsem sons will be asked to be a godfather to Prince George.
For several years, Hugh and his Dutch wife Emilie were Sandringham neighbours of the royal family as the leaseholders of Anmer Hall — the 10-bedroom Georgian property was earmarked earlier this year as a country retreat for William, Kate and Prince George.
After their lease expired, the van Cutsems moved into a country house on their own estate at Hilborough, near Swaffham in Norfolk.