There was a huge falling out between the Van Cutsems and the Prince of Wales when Edward Van Cutsem got married. The Queen was going and so was the Prince of Wales - and Camilla (pre Duchess days). The Duchess of Westminster (the bride's mother) telephoned the Prince and said that she would have to seat him with the rest of the Royal Family and that Camilla would be on the other side of the church, furthur back. Protocol was the main reason and I believe another reason given was that Camilla was either closer to the Grosvenors or the Van Cutsems. Whichever family it was, it would mean that she'd be on the opposite side to Charles. Camilla is said not to have minded but Charles was furious and the rumour (about 90% confirmed) travelled like wild-fire along the grape-vine - that rumour being that the Duchess of Westminster had hurled abuse at Charles on the telephone saying that it wasn't his wedding and he'd have to sit where he was told. So Charles said he wouldn't go if Camilla wasn't allowed to sit with him. Camilla then cancelled and said she wouldn't be going either. So, Charles telephoned Emilie Van Cutsem and asked her to intervene. She wouldn't and so they had a falling out. When Hugh (jr) Van Cutsem got married, Charles and Camilla (then married) declined the invitation.
Now alot of that is hear-say and is what I've been told by various people so you're free to believe it or disbelieve it.