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 was awarded an honorary doctorate of literature by her sister-in-law Princess Anne in a rare joint engagement as the pair were all smiles on the red carpet.

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

Queen Camilla was presented with a special honor by none other than her sister-in-law, Princess Anne. Camilla, 77, was awarded an honorary doctorate of literature by The University of London on Wednesday0.