I have recently come across the British Library Online documents and there are some very old maps, drawings etc to do with the local castles and the area. I was particularly pleased to see the OS field book sketch for Deal area drawn in 1797, but updated circa 1815. The first version was not updated, but is only available at the British Library. I have a scan of this and it is very interesting to compare with the modified one.
See Deal area 1797 (revised)
Maps
Summary:
British Library maps