Kate Middleton, Prince William News: Why the Royals Can't Sign Autographs or Eat Shellfish

Anyone asking Kate Middleton or Prince William for an autograph will always be turned down. The Duke and Duchess of Cambridge also cannot eat shellfish at public engagements.

For centuries, protocol dictates that members of the royal family cannot sign autographs even if people ask politely to lessen the chances of their signatures getting forged. There is also logic in such a rule because some people make money off the signatures from the royals or commit fraud because of it.

On eBay, a Christmas card with the Queen's signature is reportedly going for about $1,600.

Prince Charles was once heard turning down a request to sign an autograph by simply apologizing that he was not allowed to do so. But he broke the rules once in 2010 during a visit to flood victims, where he obliged a couple. The prince wrote "Charles 2010" on a piece of paper given to him, much to the surprise of the staff that accompanied him.

Staff members usually sign guest books of official engagements on behalf of the duke and duchess. But on rare occasions, Middleton has been seen signing only as "Catherine" or "Duchess of Cambridge" since marrying Prince William. She doesn't sign with a family name.

Meanwhile, the royals are also banned from eating shellfish during royal engagements, especially if it takes place abroad. The rule exists so that they won't have to deal with food poisoning or stomach upset on their trips.

The royal entourage usually requests that no tap water, underdone meat and foods with garlic be served to the duke and duchess. During the time of Princess Diana, garlic was strictly prohibited since she constantly needed to talk to people and be with them in close proximity.

Each year, the royals go to at least 2,000 official engagements hence these protocols have to be strictly observed and followed for their protection.