Between the years 1797 and 1804 Dover Castle underwent a major redevelopment building phase to make it ready for defending Dover against the very real threat of a French invasion.  Part of this major refit included the construction of four large outerworks; Hudson’s Bastion, Horseshoe Bastion, Constable’s Bastion and East Arrow Bastion.  A bastion is a platform on which heavy artillery can be mounted, and these new features gave extra firepower to the Castle.

The bastions were connected to the castle’s interior via communications tunnels and caponiers were added around the castle to reinforce firepower into the surrounding ditches.  The underground casemated barracks were also constructed in this period.

The castle’s defences were inspected again in the 1850’s and further modifications were made.

Hudson’s and Horseshoe Bastions are on the eastern side of the castle.  They are both reached via brick lined tunnels and the ditch between them is protected by means of musketry caponiers. The approach to Hudson’s was changed in the 1850’s by the construction of another caponier as artillery continued to develop and change.