Pillbox 063, Central (Old Vehicular Ferry Pier) [1939-????]
Update: Rob has identified this as Pillbox 063]
Although the wartime maps don't show the location of pillbox 061, we're guessing this is where it was.
The red marker shows the approximate location of the northern tip of the western arm of the old vehicular ferry pier. You can see the pillbox on this photo of the ferry pier in the 1950s: