This long-awaited publication elucidates a remarkable monument,now preservedin situbeside the Tower of London. Excavations at Tower Hill in 1979 uncovered substantial reamins of the medievalpostern gate at the junction of the City's defensive wall and themoat of the Tower of London. The postern gate was constructedbetween 1297 and 1308, towards the close of the reign of EdwardI. It formed a defensible terminus to the City wall and a minorgateway suitable for pedestrian traffic. The base of arectangular tower survived on the south side of the gate passage,along with a staircase turret. The structure had a cellar and aground floor chamber with a suspended timber floor, thesuperstructure surviving to the level of the arrow loops. Thetower must have had at least one upper floor. These remarkableremains survived because of a dramatic landslip in 1431 or 1440,when the southern part of the structure slipped at least threemetres down the side of the moat. The northern part of the gateprobably remained standing whilst the underpinned southern towerprovided the foundation for a rebuilt postern gate. Cartographicevidence shows that a postern gate stood on the site until atleast the 17th century. Thematic aspects include documentaryevidence that the gate was administered by the City rather thanthe nearby royal castle, the question of whether there was aRoman gate in the adjascent city wall, the appearance of thegateway and the character of the Tower Hill area in the 16th and17th centuries.