The Constable of the Tower is the most senior appointment at the Tower of London. In the Middle Ages a constable was the person in charge of a castle when the owner - the king or a nobleman - was not in residence. The Constable of the Tower had a unique importance as the person in charge of the principal fortress defending the capital city of England. He is the 159th Constable; although the precise number of Constables is uncertain, but 159 is the number arrived at after an estimate during the last century. More information on the Wikipedia page [1]