Hi all, it's been a while since I posted anything on Yo! - due to its change in format. It's nice to be back though. Hopefully I can contribute a little towards Yoliverpool's excellent and growing archive of Liverpool history. Let's start with...
In the first image I've superimposed a plan of the castle over an 1864 map of Derby Square. Notice that the tower of St George's Church, which had to be taken down due to structural subsidence, was built directly over the moat (highlighed in tone). The original builders of St George's Church hadn't excavated down deep enough to reach the bottom of the moat's sandstone bedrock, hence the later structural problems and subsequent rebuild; a lesson learnt by later builders (see image 3).
The castle moat also influenced the later street planning around Derby Square, notice the 'kink' on Preeson's Row, which originally had to step around a row of medieval houses that had enchroched upon the s/w corner of the moat.
An artist's impression of what the castle, Pool and Mersey looked like in medieval Liverpool. I've added the James Street tunnel to the illustration. It was used as a secret passage for shuttling supplies to and from the castle and the Mersey shoreline. And also very useful if the castle was under seige and its occupants had to make good their escape via the river. The moat was thought to to dry although would have collected some rainwater.
These two former bank buildings on Derby Square have sub-basements (an extra level of basement) necessary because the foundations belonging to each had to go down to the bottom of the medieval moat.