The tower of the constable is one of the towers of the first fortification of the Tower of London, the tower created by Henry III between 1234 and 1274. These great works were intended to transform the dungeon, properly protected but simply, into an impregnable fortress.
The Constable of a stronghold was his commanding officer, his manager, the person in charge of it. It was his duty to keep the fortress in a position to support a siege as well as to foresee unannounced military exits. He was an important personage, usually appointed by the king. The first constables of the Tower of London were close friends of William of Conqueror. The burden being hereditary, it is the same family that kept it a few decades.
Of course, the Constable Tower was the one where he lived. More than a fortress, Henry III, when he made his heavy modifications to the Tower of London, transformed it into a palace, that is to say that the towers he created were real apartments with the living room, the bedroom, the kitchen, a cellar, and of course ... prison cells.
This tower has a D-shaped plan, like several other towers of that time. The flat part is on the citadel side, the circular part on the outside, which improves the work of the archers.
The map of the tower of London with the list of the buildings