Part of Edward I's
expansion of the castle to the south, the Well Tower protected the new river frontage as well as guarded the cross wall, which has since been demolished between it and the Salt Tower. The origin of its name probably stems from the presence of two shafts used for drawing up water.
Rumour has it that some prisoners were chained into one of these wells and remained there over the course of three changes of the tide. However, this may be unlikely as evidence shows that this form of execution was reserved for pirates and would have taken place down river at a place called Execution Dock.