Which of these tasks do the Yeomen of the Guard famously perform before every State Opening of Parliament?

The State Opening of Parliament is an event which formally marks the beginning of a session of the Parliament of the United Kingdom. It includes a speech from the throne known as the Queen's Speech (or King's Speech). The State Opening is an elaborate ceremony showcasing British history, culture and contemporary politics to large crowds and television viewers.

First, the cellars of the Palace of Westminster are searched by the Yeomen of the Guard in order to prevent a modern-day Gunpowder Plot. The Plot of 1605 involved a failed attempt by a group of provincial English Catholics led by Robert Catesby to blow up the Houses of Parliament and kill the Protestant King James I and aristocracy. Since that year, the cellars have been searched, now largely, but not only, for ceremonial purposes.