What is the role of the Sergeant-at-Arms?

In 12th century, the role of the Sergeant-at-Arms was to protect the King or Queen by using the mace as a weapon. Today, the Sergeant-at-Arms is in charge of ceremonially carrying the mace into and out of the chamber at opening and closing of each sitting day. He or she is also responsible for safeguarding the mace, keeping order in the Public Gallery, directing Pages, ensuring the security of the chamber, and protecting Members and staff.