Camilla, 77, and Anne have grown close since Her Majesty joined the royal family in 2005 following her wedding to King Charles.

Queen Camilla donned a ceremonial robe as she received an honorary doctorate at the University of London Nov. 20, given to her by none other than her sister-in-law, Princess Anne. Camilla is being recognized for her work with literacy and literature.

Queen Camilla's attempt to break royal protocol was halted by Princess Anne during a rare joint engagement. Anne presented her sister-in-law with an honorary doctorate Wednesday.

Princess Anne is not going to break royal protocol, not even for Queen Camilla. King Charles III's sister and wife made a joint appearance at the University of London Nov. 20, where Anne, the school's Chancellor,

Princess Anne and Queen Camilla conducted a joint engagement on Wednesday, where the Queen asked her sister-in-law to break royal protocol - but Anne had a hilarious response

Princess Anne, who is widely known as the hardest working royal, appears to also be a stickler for the rules because, the royal just refused to break protocol even with Queen Camilla's permission. On Wednesday,

The two women took part in a rare joint engagement at the University of London, where the Princess Royal presented her sister-in-law with an honorary doctorate