Royal Hostage

This afternoon I attended a luncheon hosted by the Queen's Vice Chamberlain of the Household, a junior government minister whose job is to be the monarch's link with the House of Commons. His role involves weekly audiences with the Queen, not unlike the Prime Minister, and he will often accompany her on special occasions. One of the job's more curious responsibilities is being held hostage. That's right, each May when Her Majesty rides to the House of Lords to open Parliament, the Vice Chamberlain remains at Buckingham Palace as a hostage until she returns. It goes back to the civil war, when the monarch and parliament fought each other. The hostage is released only when Parliament safely returns Her Majesty's person. 
I know not of any other nation's constitution which requires the taking of hostages. Our constitution was not composed by some revolutionary committee or dry academic consultation, but in the fires of fifteen hundred years of history. It's odd, but it works.