This is (allegedly) a true story.

The Queen was in her horse-drawn Landau with a visiting Head of State driving up The Mall towards Buckingham Palace.

Suddenly one of the horses let rip with a loud and smelly fart.

The Queen felt really embarrassed and said to her fellow passenger "Oh, I do beg your pardon!".

To which visiting HoS replied "That's all right, Ma'am. I thought it was one of the horses".