Bricked up tunnels, Chatham Hill, Chatham Kent. What was they for?

Question

Tunnels must be located under the great lines, on which sits the Medway Maritime Hospital. Tunnel entrances appear near the railway bridge at the bottom of Chatham Hill.

Answer 1

I did read something about disused tunnels in "Backtrack" magazine a few years back,and seem to recall those tunnels were used as a mushroom farm at one time.

Answer 2

Almost certainly they were for military use. There was a ring of forts around the Medway towns with garrisons all prepared to protect Chatham dockyard from attack during the Napoleonic wars. There were all sorts of tunnels and short cuts between them

Answer 3

It may simply be to keep trespassers out of the abandoned tunnels, which were probably former rail lines.  There could be other reasons so see what info is on the website for Chatham.