It is exactly seven minutes to ten in the evening. The Tower of London is blanketed by darkness, its cold stone walls gathering the mist from the River Thames. The Chief Yeoman Warder emerges from the Byward Tower; his face glowing yellow from the light of a single lantern. Dressed in a scarlet dress watchcoat, and armed with a sword and partisan, the Chief Warder carries the Queen's Keys in his hand. He walks slowly toward the Bloody Tower, boot heels echoing on cobblestone, while all sentries and guards present arms to the Queen's Keys. An escort consisting of a sergeant and a drummer march to the outer gate. On the way, the Chief Warder closes and locks the heavy oaken doors of the Middle Tower and the Byward Tower, while the stony-faced escorts halt and present arms. Returning along Water Lane toward Wakefield Tower, a lone sentry waits at the Archway leading into the Bloody Tower. As the Chief Warder approaches, the sentry calls, "Halt!" The escort stops as the raspy cry of a raven comes out of the blackness. "Who comes there?" the sentry barks. "The Keys," answers the Chief Warder. "Whose Keys?" "Queen Elizabeth's Keys." "Pass Queen Elizabeth's Keys," comes the order. "All's well." The Chief Warder and his escort proceed to the steps by the 13th century wall, where the Night Guard approaches under the drawn sword of an officer. Chief Warder and his escort stop. The officer calls, "Guard and Escort, present Arms." Taking two steps forward, Chief Warder raises his bonnet in the air and proclaims, "God preserve Queen Elizabeth." "Amen!" the Guard replies. The clock chimes ten o'clock. The Drummer puts a bugle to his lips, and sounds the Last Post. A scene from a historical novel? No -- known as the Ceremony of the Keys, this is one of the oldest enactments of this kind, having been conducted every night at the Tower for approximately seven hundred years. By simply writing for permission, tourists to London can view the ancient rite in person. Some historians believe the ceremony originated at the time of the building of the White Tower, begun by William the Conqueror and completed around 1080 AD. In earlier days, the Tower was not only used as a residence for the Royals; the country's riches were stored there, as well. Many political figures were imprisoned at the Tower and often the people outside the Tower's walls were not always in agreement. Enemies of the king often tried to steal the Crown Jewels and attempt to free political prisoners, so the need for more security became obvious. Since the Tower's beginnings there have been men to guard prisoners and attend the gates, but the Body of Yeoman Warders claim their origins from the first year of Henry VII's reign. The traditional ceremony of locking up the Tower of London is said to predate the Warders. Every evening the Gentleman Porter - now known as Chief Yeoman Warder - along with an armed escort, locked and secured all the gates and doors leading into the Tower. The Keys would then be handed to the Tower Governor, who kept them through the night. Today Yeoman Warders are recruited from the Royal Marines, the Army and the Royal Air Force and must have attained the rank of Warrant Officer, Staff Sergeant or Flight Sergeant. They control all gates and Wharf and all areas open to the public. Currently, between 30 and 40 Yeomen live at the Tower. Their duties include guarding prisoners (although there are no prisoners held at the Tower at present) and attending, or waiting, the gates. The original term "Yeoman Waiters" has since been dropped and the term Warder is used to describe all. The daily roster is still called "the Wait". The Duke of Wellington, who acted as Constable of the Tower in 1826, made an order that the time of the locking of the gates would be set at ten o'clock to ensure his soldiers entry into the Tower every night. Dignified in its magnificence, the Tower of London continues the pattern of traditional pageantry into the 21st century. Still a castle and cache for some of the Queen's riches, the Tower blends new-age tourism with a need for security by continuing its nightly closing with the Ceremony of the Keys.

If You Go: The Tower of London is open March through October, Monday through Saturday from 9 a.m. to 5 p.m., and Sunday 10 a.m. to 5 p.m. November through February, hours are Tuesday through Saturday, 9 a.m. to 4 p.m., and Sunday and Monday 10 a.m. to 4 p.m. The Tower is closed Christmas Eve, Christmas Day, Boxing Day (Day after Christmas) and New Year's Day. Admission Prices (In English Pounds): Adults 10.50 Students and seniors 7.90 Children 5 to 15 yrs 6.90 Children under 5 are free Family ticket (2 adults, 3 children) 31.00 Tickets for the Ceremony of the Keys are free, but must be reserved in advance. Requests can be made by writing to: Ceremony of the Keys Tickets, Tower of London, Tower Hill, EC 3N 4AB, London, England. For more information, call 0171-709-0765