
Entertaining members of the Royal Family must be pretty nerve-wracking, particularly as a plethora of rules are usually enforced. According to a royal author, one former American president was "horrified" during a visit from King Charles for a slightly embarrassing reason.
Speaking to Hello! magazine, David Charter—author of Royal Audience: 70 Years, 13 Presidents—One Queen's Special Relationship With America—explained, "Ronald Reagan was horrified when he had Prince Charles into the Oval Office and they brought him a cup of tea that still had the tea bag in it, and he could see that he wasn't drinking this cup of tea, and he thought he'd made a terrible faux pas."
Luckily, according to Charter, the "tea bag" debacle would be considered "a very small little faux pas" to members of the Royal Family. After all, a simple mistake is likely to "somehow only endear each side [the British and Americans] to the other a little bit more," Charter noted.

Per Hello! magazine, Reagan reflected on the error in a diary entry written on May 1, 1981. "He's a most likable person," Reagan said of Charles. "The ushers brought him tea—horror of horrors they served it our way with a tea bag in the cup."

He continued, "It finally dawned on me that he was just holding the cup and then finally put it down on a table. I didn't know what to do." According to Reagan, Charles later responded by saying, "I didn't know what to do with it."
So, if you're entertaining a member of the Royal Family anytime soon, remember to remove the tea bag from the cup before serving as a matter of importance.