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

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, Camilla was presented an honorary doctorate of literature by her sister-in-law Princess Anne.

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 and Queen Camilla made a rare public appearance together earlier this month, with one expert claiming the Princess Royal showed her true feelings

Queen Camilla returned to royal duties for the first time since Buckingham Palace announced she had been diagnosed with a chest infection which affected her timetable

Queen Camilla and Princess Anne appeared at a rare joint engagement tonight in London for a very special reason.

Queen Camilla suffered a setback in November as she was forced to back out of numerous royal engagements due to a chest infection, but now that she's back to work, the Queen has been keeping plenty busy—and one member of the Royal Family has stepped up to present her with a touching honor.

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

Her Majesty Queen Camilla was made an honorary doctorate of the University of London by the college's Chancellor, Princess Anne, on Wednesday, November 20. However, the important event was not without some humor as the Princess Royal found a royal protocol breach request from the Queen "hilarious.

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,