For 350 years, coal-black ravens have wandered freely around the Tower of London's grassy inner courtyard as cawing barometers of the monarchy's vitality -- if the ravens ever die or leave the tower, the legend goes, the tower and the kingdom will fall.

Now the fear of bird flu has done what Luftwaffe bombings, blizzards, assassinations and abdications could not, forcing the ravens to be moved inside in isolation for their own safety and to hedge Britain's bets on the future of the crown.