Whose Keys? King George's Keys. Every night, an hour before midnight, the Yeoman Porter, escorted by a guard, proceeds to lock up the Tower doors, after which he goes to the guardhouse, where a sentry challenges him with "Who goes there?" "The Keys." "Whose Keys?" "King George's Keys." "Advance, Keys," whereupon the Yeoman Porter cries, lifting his hat, "God preserve King George V.," while guard and escort present arms.