Every night, a semi-secret ceremony takes place at the Tower of London. In-the-know onlookers wait in silence to watch as the fortress’s huge wooden doors are shuttered and secured, a ritual that has taken place here for roughly 700 years.

Attendees are admitted at precisely 9:25 p.m. via the main entrance of the Middle Tower. A Beefeater or Yeoman Guard will then escort you through the Byward Tower on a short mini-tour, walking first through the ancient portcullis with its “murder hole.”

You’ll walk carefully along the cobblestones past the Traitor’s Gate and the nearby Wakefield Tower, where Henry VI was murdered. As you wait for the action to start at precisely 9:53 p.m., you will, if necessary, be told loudly to remain quiet. It makes for some suspense until four soldiers escorting the lantern-carrying Chief Warden, who has just closed the Byward Tower, come slowly into view.

After much pomp and circumstance, you will hear the cry of “ladies and gentlemen, the Tower is secured for the evening” ringing out. At 10 p.m. sharp, the ceremony ends, and you’re quickly escorted back out onto the busy London streets.