Visiting the Queen

Last full day with our house guests. I am exhausted! We were excited to see the armed guards come out preparing for someone important to arrive at Buckingham Palace. He told us that it was the Queen's sister, however, I understand that she passed away in 2002. I am just wondering...was he trying to pull one over on us or did he just not know who she was? According to the flag on the top of the palace, the Queen was not home, so I couldn't ask her who it was either!