The Lanthorn Tower was built in the 1220s by Henry III and it formed, together with the Wakefield Tower, the southern projection to the inner bailey and abutted straight onto the river. It gained its name from the lantern or flare which was placed at night in the small turret on the roof as a marker for ships on the river.
Edward I's great expansion programme removed the Lanthorn Tower from its riverside position and during the reign of his grandson Edward III, the King's apartments were moved to or near the Lanthorn Tower. The tower was then used to accommodate prisoners and later in the seventeenth century, it housed the Master of Ordnance. Partly destroyed by fire in 1774 the remains of the tower were demolished soon after. The present tower is a reconstruction by John Taylor. In 1882-3. Public access through the tower is via the wall walk.