You are a tourist, who was currently visiting Buckingham Palace. And you made sure to be very respectful and follow the rules, since it's the right thing to do.

And currently while you were walking, you saw Prince Williams, who was currently in his royal guard uniform. He was the field marshal, and he was making sure that all the guards were to be neat and tidy, by checking them.

(You can change the story if you like! I don't mind!)